The quantity of atoms or molecules per gram of atomic weight is known as aspartame number, which is 6.022 1023/mole.
A dipeptide made up of the amino acids phenylalanine and aspartic acid is called aspartame and is its methylester. People with phenylketonuria, who must carefully limit their intake of phenylalanine, must be made aware of the ingredient's existence in the medicinal product and the quantity present in each dose unit. In turn, 10 g of aspartame contains 0.034 moles of molecules. How many nitrogen atoms make up 1.2 grams of aspartame? Due to aspartame's 294.347 g/mol molar mass, 1.2 g is equal to 1.2 g / 294 g/mol, or 0.0041 moles. Aspartame is digested in the body, unlike certain other potent sweeteners, and as a result.
To learn more about aspartame please click on below link
https://brainly.com/question/26876807
#SPJ4
An oxide of chromium crystallizes with the following unit cell (chromium = gray; oxygen = red)(Figure 1) .
What is the formula of the oxide?
An oxide of chromium crystallizes with the following unit cell (chromium = gray; oxygen = red)(Figure 1) --CrO3
In order to determine the formula of the oxide, we need to determine the ratio of chromium to oxygen atoms in the unit cell. From the provided unit cell, we can see that there is one chromium atom (gray) in the center of the unit cell, and four oxygen atoms (red) surrounding it. This gives us a ratio of 1:4 chromium to oxygen, which simplifies to a ratio of 1:4 or 1/5. Therefore, the formula of the oxide is CrO4.An oxide is a chemical compound that contains at least one oxygen atom and one other element. Oxides can be either inorganic or organic, depending on the element that is combined with oxygen. Inorganic oxides are compounds composed of a metal and oxygen. They can be further classified as acidic, basic or neutral depending on the oxidation state of the metal atom. Examples of inorganic oxides include water (H2O), carbon dioxide (CO2), sulfur dioxide (SO2), and nitrogen dioxide (NO2)
To learn more about oxide here:
https://brainly.com/question/9496279
#SPJ4
Coca-Cola is making a version of Coke that uses sucrose (C12H22O11) instead of high fructose corn syrup. If there are 39.24 grams of sucrose in a 12.0 fluid oz. can of this Coke, what is the molarity of sucrose in the Coke
Coca-Cola is making a version of Coke that uses sucrose (C12H22O11) instead of high fructose corn syrup. The molarity of sucrose in the Coke is 0.32 mol/L.
Coca-Cola is making a version of Coke that uses sucrose (C12H22O11) instead of high fructose corn syrup. If there are 39.24 grams of sucrose in a 12.0 fluid oz. can of this Coke, what is the molarity of sucrose in the Coke.
To find the molarity of sucrose in the Coke, we first need to find the number of moles of sucrose present in the can. We can use the mass of sucrose (39.24 g) and the molar mass of sucrose (342.3 g/mol) to find the number of moles of sucrose:
= (39.24 g) / (342.3 g/mol)
= 0.114 mol
Next, we need to find the volume of the can in liters. We can convert the volume in fluid oz. to liters using the conversion factor 1 fluid oz.
= 0.0295735 L:
= (12.0 fluid oz.) x (0.0295735 L/fluid oz.)
= 0.354882 L
Finally, we can use the formula for molarity (moles of solute / liters of solution) to find the molarity of sucrose in the Coke:
= molarity
= (0.114 mol) / (0.354882 L)
= 0.32 mol/L
To know more about molarity please refer: https://brainly.com/question/8732513
#SPJ4
How many mole is 1g?
One gram of a chemical is equivalent to one mole.
A physical characteristic called the molar mass is calculated by dividing the mass of a given substance by the substance's volume. The standard relative atomic mass of an element is multiplied by the molar mass constant, 1 × 10⁻³ kg/mol = 1 g/mol, to determine the molar mass of its atoms. A compound's molar mass is calculated by adding the standard atomic weights of the constituent atoms and multiplying the result by the molar mass constant.
One atom or molecule has the same mass in grams as one mole of a substance does in atomic mass units.
To know more about mole click here
https://brainly.com/question/15356425
#SPJ4
Mg + _________HCI →
_____ H₂ + _____ MgCh
Mg + 2HCl → H2 + MgCl2 because The reaction between magnesium and hydrochloric acid produces hydrogen gas and magnesium chloride.
What is molecule?Molecules are the smallest unit of a chemical compound that can exist independently and remain unchanged in chemical composition. A molecule is composed of two or more atoms that are chemically bonded together. A molecule can be made up of different elements, such as carbon, hydrogen, oxygen, and nitrogen, and can be composed of a variety of combinations of these elements. Molecules are essential components of all living things, as they are important for basic functions such as energy transfer, metabolism, and cell structure.
To learn more about molecule visit:
brainly.com/question/475709
#SPJ1
If the actual yielsd of a reaction is 50 g and the theoretical yield is 60 g. What is the percent yield.
If the actual yield and percent yield are 51.4g and 77.0%, respectively, calculate the theoretical yield. We predicted a theoretical yield of 13 grams for the reaction of Na with Cl2.
Yield is determined by dividing the principal amount by the net realized return. Gains and returns on stock investments, for instance, can take one of two kinds. On the basis of the chemical equation's stoichiometry, theoretical yield is computed. Experimental data are used to determine the real yield. Calculating the ratio of actual yield to theoretical yield yields the percent yield. The % ratio of the theoretical yield to the actual yield is known as the percent yield. It is calculated as the theoretical yield multiplied by 100% divided by the experimental yield.
Learn more about reaction here-
https://brainly.com/question/28984750
#SPJ4
If there are 6 atoms of hydrogen on the products side, how many molecules of H2 are on the reactants side?
If there are 6 atoms of hydrogen on the products side, then there would be 6 atoms of hydrogen also on the reactants side. That would be 3 molecules of [tex]H_2[/tex].
Law of conservation of atomsAccording to the law of conservation of atoms or matter, atoms can neither be destroyed nor created during the course of chemical reactions. However, atoms can change forms during reactions.
Going by this law, it means the number of atoms of a particular element must remain constant before and after chemical reactions. Otherwise, we will say the chemical equation of such reactions are not balanced.
Thus, if there are 6 atoms of hydrogen on the products side of a reaction, 6 atoms of hydrogen must also be on the reactants side of the reaction. A molecule of hydrogen, [tex]H_2[/tex], has 2 atoms of hydrogen. This means 3 molecules of hydrogen must be on the reactants side in order to have a total of 6 hydrogen atoms.
More on law of conservation of atoms can be found here: https://brainly.com/question/2175724
#SPJ1
What is the evidence for Darwin's theory of evolution?
The evidence for Darwin's theory of evolution is the consistency of the sequence of fossils from early to recent.
Changing populations and species of organisms are at the heart of biological evolution. The British naturalist Charles Darwin is most likely the first individual that comes to mind today when we discuss evolution. The biological evolution via natural selection theory was put out by British biologist Charles Darwin. Darwin believed that species change over time, give rise to new species, and descended from a single ancestor through the process of evolution. Charles Darwin's theory of evolution is known as natural selection. Animals with heritable qualities that aid in survival and reproduction will often generate more offspring than their contemporaries due to the limited resources in nature, increasing the frequency of such traits through subsequent generations.Populations change throughout time through natural selection, becoming increasingly adapted to their surroundings. Natural selection is reliant on the environment and necessitates the presence of heritable variation within a population.
Learn more about Darwin's theory of evolution
brainly.com/question/25718754
#SPJ4
What process makes 2 ATP?
Anaerobic respiration results in the production of 2 ATP molecules.
What is anaerobic respiration?Anaerobic respiration is the use of electron acceptors other than molecular oxygen in respiration. Despite the fact that oxygen is not the ultimate electron acceptor, the process employs a respiratory electron transport chain. When there is insufficient oxygen for some species to respire, they still require energy to survive. Due to a lack of oxygen, they respire in the absence of oxygen to create the energy they require, which is known as anaerobic respiration. While most aerobic respiration (with oxygen) occurs in the cell's mitochondria, anaerobic respiration (without oxygen) occurs in the cytoplasm.
Here,
Two ATP molecules are created during anaerobic respiration.
To know more about anaerobic respiration,
https://brainly.com/question/12605249
#SPJ4
how many grams of KNO3 that should be placed in the airbag to fully react with the Na.
10 Na + 2KNO3 > 1K20 + 5Na2O + 1 N2 (g)
How many times more acidic is a solution with a pH of 2 compared with one with a pH of 5 Explain.
Using a logarithmic scale with 7 as neutral, lower values are more acidic and higher values are more alkaline, the acidity or alkalinity of a solution is expressed. where c is the number of moles of hydrogen ions present per litre. So pH 2 is 1000 times stronger than pH 5, and vice versa.
A pH of 2 is how much more acidic than a pH of 5.For instance, a pH of 2 is 10,000 times more acidic than a pH of 3 and a pH of 5 is 10,000 times more acidic. Ten times as alkaline as a pH of 10 is a pH of 11.
How many times more acidic is a pH 2 solution compared to a pH 9 solution?Each whole pH value is ten times more acidic than the next higher value since the pH scale is logarithmic.
To know more about pH visit:-
https://brainly.com/question/15289741
#SPJ1
Why does fluorine react with xenon but iodine does not?
Fluorine reacts with xenon but iodine doesn't because fluorine is highly electronegative, it can pull electrons from xenon which is a noble gas and rarely reactive. On the other hand, iodine has low electronegativity and is least reactivity, so doesn't react with xenon.
Fluorine and iodine belongs to the family of halogens with the general electronic configuration ns²np⁵ . So, they have the tendency to attract electrons in their valence shell. Xenon, on the other hand is a noble gas with a stable electronic configuration ns²np⁶.
In family of halogens, Fluorine has the highest electronegativity and iodine has the least due to increase in its size. So, more electronegative fluorine has the tendency to form compounds with xenon whereas both iodine and xenon being less reactive cannot form a bond together.
To know more about reaction of fluorine with xenon here
https://brainly.com/question/2269881
#SPJ4
Why are all the elements in group 18 relatively unreactive meaning they do not gain lose or share electrons with other atoms?
Elements of group 18 belongs to the family of noble gases with a general electronic configuration ns²np⁶, where the valence shell is completely filled.
The elements of group 18 are considered to be noble because they have a completely filled valence shell due to which they donot have the tendency to gain, lose or share their valence electrons with other atoms. Thus, they are highly unreactive.
The elements belonging to noble gas family are: Helium (He), Neon (Ne), Argon(Ar), Krypton(Kr), Xenon(Xe), Radon(Rn).
under conditions of standard pressure and temperature, these elements exists as gases with very low chemical reactivity so they are known as inert gases.
To know more about group 18 elements here
https://brainly.com/question/29355055
#SPJ4
How is water an exmaple of an molecule and a compound
Answer:
Water is a compound because it is made up of water molecules. There is no such thing as water atoms. Water molecules are made of hydrogen and oxygen atoms, in the definite proportion of two hydrogens for one oxygen.
Explanation:
The difference between a molecule and a compound is this:
A molecule consists of two or more atoms joined by a chemical bond.
A compound consists of two or more different atoms joined by chemical bonds.
Water (H2O) is both a molecule and a compound.
Hydrogen gas (H2) and oxygen gas (O2) are molecules but because the atoms of which they are made are not different, they do not qualify as compounds.
An ice cube with a volume of 45. 0ml and a density of 0. 9000g/cm3 floats in a liquid with a density of 1. 36g/ml. What volume of the cube is submerged in the liquid
The volume of the cube that is submerged in the liquid would be 36.0 ml.
What is submerged?Submerged refers to something that is completely covered or surrounded by a liquid, usually water. Submerged objects are often completely or partially underwater, and can refer to anything from a submerged shipwreck to a submerged rock formation. Submerged objects can also refer to objects that are partially or totally surrounded by the water or liquid, such as a submerged tree or submerged vegetation. Submerging can also refer to objects that are pushed underwater or forced down due to pressure, such as a submarine. Submerging can also refer to a process in which an object is submerged and then brought back up, such as in underwater welding or archaeological excavations.
To learn more about submerged
https://brainly.com/question/15109453
#SPJ4
What reagent causes the observed visual change in a positive Lucas test?
The observed visual change from a clear and colourless characteristic to a turbid, cloudy, and hazy characteristic, in a positive Lucas test, is caused by the Lucas reagent.
The Lucas Test is used to detect the presence of a primary alcohol.
When the test is positive, the mixture of the primary alcohol with the Lucas reagent changes from a clear and colourless characteristic to a turbid, cloudy, and hazy characteristic. This visual change is due to the reaction of the primary alcohol with the Lucas reagent which is a mixture of concentrated hydrochloric acid and zinc chloride.
The Lucas Test is used to detect the presence of a primary alcohol, and when a positive result is obtained, the reaction of the primary alcohol with the Lucas reagent, a mixture of hydrochloric acid and zinc chloride, causes the visual change from a clear and colourless characteristic to a turbid, cloudy, and hazy one.
learn more about lucas test here
https://brainly.com/question/14687410
#SPJ4
PLS HELP ASAP PLSSSS
Which supports the idea that conservation of mass is a scientific law instead of a hypothesis?
A- It is an educated guess.
B- It has been tested and supported once or twice.
C- It has been examined, tested and supported over centuries.
D- It has been tested many times and sometimes is true and sometimes isn’t.
Answer:
C- It has been examined, tested and supported over centuries.
Explanation:
The conservation of mass is a scientific law that states that matter cannot be created or destroyed, only transformed from one form to another. This law has been extensively tested and supported over centuries of scientific investigation, and it is considered to be a fundamental principle of chemistry and physics.
Consider the reaction.
NH4HS(s)⇌NH3(g)+H2S(g)
At a certain temperature, Kc=8.5×10−3. In a reaction mixture at this temperature containing solid NH4HS, [NH3]=0.166 M and [H2S]=0.166 M. Will more of the solid form or will some of the existing solid decompose as equilibrium is reached?
In the reaction, NH4HS(s)⇌NH3(g)+H2S(g), more of the solid will form.
What is equilibrium?In a chemical reaction, equilibrium is the state where both the reactants and products are present in concentrations which have no further tendency to change with time, so there is also no observable change in the properties of the system. This state results when forward reaction proceeds at the same rate as reverse reaction.
If Q= K then equilibrium
Q>k, then reversed direction shift
Q<k, then forward direction shift
Given, Kc=8.5×10−3
Given [NH3]=0.166 and M [H2S]=0.166 M
Here Q= 0.166 M (given)
It shows Q> k that is 0.166 > 8.5×10−3
Therefore, more of the solid will form.
To know more about chemical equilibrium, refer
https://brainly.com/question/8869462
#SPJ4
if you start with 5.5 grams of sodium fluoride how many grams of magnesium fluoride will be produced
From 5.5 grammes of sodium fluoride, 4.1 grammes of magnesium fluoride will be created. The inorganic substance MgF2 stands for magnesium fluoride.
It naturally occurs as the rare mineral sellaite and is a white crystalline salt that is transparent over a broad range of wavelengths and has commercial use in optics used in space telescopes. With the formula NaF, sodium fluoride (NaF) is an inorganic substance. It is utilised in minute quantities in toothpaste, metallurgy, and as a flux in addition to fluoridating drinking water. It is a white or colourless substance that easily dissolves in water. Pharmaceutical manufacturers frequently use it as a source of fluoride. Mass in grammes is equal to 0.06548 times 62.301 grammes of MgF2.
= 0.06548 /62.301 = 4.1grams
Learn more about sodium fluoride here
https://brainly.com/question/2807538
#SPJ4
What is the measurement of expired CO2 that typically provides a numeric display of the partial pressure of CO2 in torr or mmHg
The measurement of expired CO₂ that typically provides a numeric display of the partial pressure of CO₂ in torr or mmHg is the capnometry.
The capnometry measurement of the CO₂ , carbon dioxide is the measurement in the expired air and it provides the clinician with the noninvasive measurement of systemic metabolism and the ventilation. it is used to determine the correlation in between the tidal CO₂ and the partial CO₂ in the non intubated breathless patents.
Thus, the measurement if the expired CO₂ that shows the partial pressure of the CO₂ is the capnometry.
To learn more about pressure here
https://brainly.com/question/9226237
#SPJ4
A(n) ____________________ has more hydrogen ions than hydroxide ions and has a pH ____________________ 7.
An acidic solution has a pH over 7 and contains more hydrogen ions than hydroxide ions. Any aqueous solution with a pH lower than 7.0 ([H+] more than 1.0 x 10-7M) is said to be acidic.
A acidic solution that uses water as its solvent is said to be aqueous. Acidic solutions are sour in contrast to alkaline solutions, yet it's never a good idea to taste an unidentified solution. Any solution that contains more hydrogen ions per volume of solution than water is an acidic solution; contrasted with acidic solutions are basic or alkaline solutions. Atomic number 1 and the letter H stand for the chemical element hydrogen. The element hydrogen is the lightest.
Learn more about acidic solution here
https://brainly.com/question/13208021
#SPJ4
Select the correct answer. which gas is the most abundant greenhouse gas?
a. ozone
b. chlorofluorocarbon
c. carbon dioxide
d. methane
e. water vapor
E) The most significant and prevalent greenhouse gas is water vapor. Ozone, carbon dioxide, methane, nitrous oxide, and other gases are also present.
Which major source of greenhouse gases is it?Over the past 150 years, almost all of the rise in atmospheric greenhouse gases has been caused by human activities. Burning fossil fuels for transportation, electricity, and heating is the primary human activity in the United States that contributes to the emission of greenhouse gases.
Which four greenhouse gases have the greatest impact?The greenhouse gases on Earth warm the planet by storing heat in the atmosphere. Carbon dioxide, methane, nitrous oxide, and water vapor—all of which are found naturally—as well as fluorinated gases—which are made—are the main gases that cause the greenhouse effect.
To learn more about water vapor here:
https://brainly.com/question/14529481
#SPJ1
How do you calculate number of molecules?
Determine the substance's molecular weight in units of one mole, then divide the molar mass value by the molecular mass, and multiply the result by the Avogadro constant to get the required number of molecules.
It is possible to determine the number of molecules by using the relationship between the number of moles and Avogadro's number, which is provided by;
1 mole = Avogadro's constant (NA)
The number of molecules will equal the product of the number of moles and Avogadro's number, which is determined after the number of moles has been determined
To know more about molecules click here
https://brainly.com/question/19922822
#SPJ4
How many moles of MgCO3 are present in 252. 939 grams of MgCO37
N
Oь
3
ос
5
Od
6
sndjxjcjcjcjchc
The number of moles of MgCO3 that is present in the given mass of magnesium carbonate is 2.99 moles.
The number of moles can be defined as the ratio of given mass over molar mass. The chemical that is given is magnesium carbonate having molar mass of 84.314 g/mol and the given mass of the same is 252.939 grams.
The formula for number of moles that is 'n' can be given as follows:
n= m/M where m is the given mass and M is the molar mass.
Substituting the values,
n= 252.939 grams /84.314 grams/mol
n=2.99 moles
Therefore, the number of moles of MgCO3 is 2.99 moles.
To learn more about number of moles check the link below:
https://brainly.com/question/23949935
#SPJ4
Write a introduction base on the topic reproduction, male an female reproduction system
The ma le repr0 ductive system includes made up of internal organs such as the prostate gland, vas deferens, as well as ure thra as well as external geni talia like the pe nis, tes tes, as well as scrot um.
The health of something like the male reproductive system and the hormo nes secreted by the brain determine a man's fertility as well as sexual characteristics.
The human reproductive system would be the organ system primarily charged of creating and fertilizing gametes (eggs but rather sperm) as well as carrying a fetus. The gonads of both se xes create gametes.
The ov aries, fallopian tubes, uterus, cervix, as well as vagina are all parts of the female repro ductive system. It comprises the pe nis, prostate, as well as tes tes in men.
To know more about repro ductive system
https://brainly.com/question/14235396
#SPJ4
Select the correct answer. what is the name of a system that converts thermal energy into a form of useful mechanical or electrical energy?
a. incubator
b. heat engine
c. centrifuge
d. vacuum column
e. spectrophotometer
Heat engine is a system that converts thermal energy into a form of useful mechanical or electrical energy.
In thermodynamics, the heat engine is a system which is able to convert the heat or thermal energy into mechanical or electrical energy which can be used in order to perform mechanical work. This is achieved by bringing the a particular working substance to a lower state temperature from a higher state temperature.
There are a different types of heat engines in which the Carnot engine possesses the maximum efficiency. Some examples of heat engines are firearms, thermal power station etc.
Hence, the correct option is b. heat engine.
To know more about heat engine here
https://brainly.com/question/28034387
#SPJ4
15.0 L of an ideal gas at 298 K and 3.36 bar are heated to 350 K with a new pressure of 4.90 atm. What is the new volume in litres
The new volume in litres is 13.29 L.
Given,
Temperature 1 (T₁) = 298 K
Volume 1 (V₁) = 15 L
Temperature 2 (T₂) = 383 K
Pressure 1 (P₁) = 3.36 atm
Pressure 2 (P₂) = 4. atm
By Ideal Gas Equation,
P₁V₁/T₁ = P₂V₂/T₂
⇒ (3.36*15)/298 = (4.90*V₂)/383
⇒50.4/298 = 4.90V₂/383
⇒ (50.4*383) / (298*4.90) = V₂
⇒ 19303.2/1460.2 = V₂
⇒13.29 L = V₂
New Volume will be 13.29 L.
Ideal gas law is a precise approximation of the behavioral of several gases under various situations in thermodynamics. The Ideal Gas Equation is a mathematical formula that combines empirical laws such as Charle's law, Boyle's law, Gay-law, Lussac's and Avogadro's law.
The equation characterizing the states of hypothetical gases stated mathematically by combinations of empirical or physical constants is known as the Ideal Gas Equation. It's also known as the universal gas equation. It is defined as follows:
"The ideal gas law seems to be the equation of state for a fictitious perfect gas. It is a decent approximation of the behavioral of various gases under numerous situations, while it has significant limitations".
To know more about the Ideal gas law, here
https://brainly.com/question/28257995
#SPJ4
an empty bottle has a volume of 2.0 L at room temperature 25 C. What will the new volume be if you put it in the freezer (-4C)
An empty bottle has volume of 2 L at room temperature 25°C . If we put it in the freezer (-4°C), the new volume will be 1.8L.
According to Charles' law, " the volume of a given amount of gas held at constant pressure is directly proportional to the kelvin temperature". The equation is represented as:
V₁/T₁ = V₂/T₂
This means, with increase in temperature, volume will also increase and vice versa.
According to question,
V₁ = 2.0 L
T₁ = 25°C = (25+273)K = 298 K
T₂ = -4°C = (-4 + 273)K = 269 K
Using Charles' law equation,
V₁/T₁ = V₂/T₂
⇒V₂ = V₁×T₂ / T₁
⇒V₂ = 2L × 269 K/298K
⇒V₂ = 1.8 L
Thus, the new volume when the bottle is put in a freezer (-4°C ) is 1.8 L
To know more about Charles' law here
https://brainly.com/question/15969029
#SPJ4
Which of these is not a property of the intracellular fluid (ICF)?The concentration of chloride ion is lower than that of interstitial fluid. The concentration of potassium ion exceeds that of sodium ion. The concentration of sodium ion exceeds that of potassium ion. The protein concentration is higher than that of interstitial fluid.
The protein concentration is higher than that of interstitial fluid. The intracellular fluid (ICF) is the fluid inside cells, and is composed of water, electrolytes, and organic molecules.
The intracellular fluid (ICF) is the fluid inside cells, and is composed of water, electrolytes, and organic molecules. Common properties of ICF include high concentrations of potassium ions and low concentrations of chloride ions compared to interstitial fluid. The protein concentration of ICF is lower than that of interstitial fluid.
The protein concentration is higher than that of interstitial fluid.
learn more about fluid here
https://brainly.com/question/28445909
#SPJ4
Which one of the following statements is not correct about MSDS?
Select one:
a.
It does not contain information on physical and chemical properties of the material, potential hazards of the material and how to work safely with these materials.
b.
It provides single reference for all information about hazardous chemicals.
c.
Material Safety Data sheet forms the important elements of effective Chemical Hazards Communication System.
d.
It is a document prepared by the manufacturers/suppliers of the chemical
Option B. It provides a single reference for all information about hazardous chemicals.
MSDS does not provide a single reference for all information about hazardous chemicals, but it does provide information on physical and chemical properties, potential hazards, and safe work practices.
Understanding the Role of MSDS in Chemical Hazard CommunicationThe Material Safety Data Sheet (MSDS) is a document prepared by the manufacturer or supplier of a hazardous chemical which provides information about the physical and chemical properties of the hazardous chemical, potential hazards associated with it, and how to work safely with it. The MSDS is an important element of an effective chemical hazard communication system as it provides information on how to identify and protect against potential health hazards, proper storage and handling procedures, and proper disposal methods.
Learn more about MSDS: https://brainly.com/question/18638385
#SPJ4