Answer:
Observational study
Explanation:
An investigation of what happened over the years to the people who were exposed to radiation during the 1986 Chernobyl nuclear disaster would be termed an observational study because it will require observing subjects and finding out if there is a kind of correlating factor in the subjects that could indicate the level of exposure to the nuclear radiation.
There are basically two types of research studies:
1. Observational studies
2. Experimental studies
Observational studies involve just the observation of subjects and trying to find out some correlation factors. This kind of study could be prospective when it deals with what could happen in the future based on certain factors or retrospective when it considers what has already happened. An observational study can be cross-sectional, case-only, case-control, or cohort study.
Experimental studies are also referred to as randomized or controlled trial studies. Here, subjects are grouped and each group receives a different treatment in order to isolate the effect of a particular factor or variable relating to the treatment.
Suppose there is a gaseous mixture of nitrogen and oxygen. If the total pressure of the mixture is 480 mmHg, and the partial pressure of nitrogen is 290 mmHg, calculate the partial pressure of oxygen in the mixture using Dalton's law.
Answer:
Partial pressure of oxygen = 190 mmHg
Explanation:
From the question;
Mixture contains only nitrogen and oxygen
Total pressure of the mixture = 480 mmHg
Partial pressure of nitrogen = 290 mmHg
Dalton's law states that the pressure of a system is as a result of the sum of the partial pressures of the individual components of the mixture. This means that in this mixture;
Pressure of mixture = Partial Pressure of Nitrogen + Partial Pressure of Oxygen
480 = 290 + Partial pressure of oxygen
Partial pressure of oxygen = 480 - 290
Partial pressure of oxygen = 190 mmHg
How many π electrons are there in adenine? State which atoms contribute one electron to the π MOs and which atoms contribute two electrons?
Answer:
12 π electrons.
Explanation:
The structure of adenine can be seen below.
From the diagram, the total number of electrons in adenine is 70 electrons where 20 of them are core electrons.
Also from this same structure, we will notice that we have a total number of 12 π electrons.
i.e.
Each one of these five atoms described takes part in the π electron. These are N-1, N-3, N-7 which comprise of 2σ bonds, and also each of three N contributes one π electron.
Similarly, N-9 and N-10 contain 3σ bonds; Hence, each of them donates two electrons.
Thus;
5C = 5π electrons
3N = 3π electrons
2N = 4π electrons
= 12π electrons
A sample of 7.4 L of NH3 gas at 22 ∘C and 735 torr is bubbled into a 0.50-L solution of 0.35 M HCl. Assuming that all the NH3 dissolves and that the volume of the solution remains 0.50 L, calculate the pH of the resulting solution.Kb for Nh3=1.8x10-5
Answer:
pH = 9.11
Explanation:
First, using gas law, we will determine the moles of NH3 bubbled. Then, with moles of HCl we can determine how many NH4⁺ are produced. As last, using H-H equation for bases we can find pOH and pH of the solution:
Moles NH3:
PV = nRT
P = pressure: 743 torr * (1atm / 760torr) = 0.9776atm
V = volume: 7.4L
n = Moles. Our incognite
R = Gas constant: 0.082atmL/molK
T is absolute temperature: 273.15K + 22°C = 295.15K
PV / RT = n
0.9776atm*7.4L / 0.082atmL*295.15K = 0.30 moles of NH3
Moles HCl:
0.50L * (0.35mol / L) = 0.175 moles of HCl
Based on the reaction:
NH3 + HCl → NH4⁺ + Cl⁻
All HCl added is producing NH₄⁺ = 0.175 moles NH₄⁺
Moles NH₃: 0.30moles NH3 - 0.175 moles = 0.125 moles NH₃
H-H equation for bases is:
pOH = pKb + log [BH+] / [B]
Where pKb = -log Kb = 4.74
[BH+] could be taken as moles of NH4+ = 0.175 mol
[B] are moles of NH3 = 0.125 mol
pOH = pKb + log [BH+] / [B]
pOH = 4.74 + log [0.175mol] / [0.125mol]
pOH = 4.89
pH = 14-pOH
pH = 9.11
A system absorbs 191 kJkJ of heat and the surroundings do 120 kJkJ of work on the system. Part A What is the change in internal energy of the system?
Answer: the change in internal energy of the system is 311 kJ
Explanation:
Given that;
A system absorbs a heat dQ = 191 kJ
And the the surroundings do work on the system dW = 120 kJ
change in internal energy of the system = ?
We take a look at the first law of thermodynamic
Initially the system absorbs energy ( dQ =1 91 kJ) as heat.
Then the surroundings do work (dW = 120kJ) on the system,
Hence the system gains 120 kJ more.
The total energy change is = heat + work
dU = dQ + dW
dU = 191 + 120
dU = 307 kJ
change in internal energy = 311 kJ
Therefore the change in internal energy of the system is 311 kJ
BaO2 is a peroxide. Why?
Answer:
jajjsjsjddjdjdjdjdjjdjeieiririitofodoslwnridooskemridisoskswkwjj jwjwiwiwiwkiwiw
Which statement describes a major drawback of the Bohr model that caused scientists to replace it?
(A) It worked only for helium and larger atoms.
(B) It did not identify the distance between an electron and the nucleus.
(C) It contradicted the Heisenberg uncertainty principle.
(D) It stated that spectral lines of atoms are similar.
on edgen
Answer:
C.it contradicted the heinsberg uncertainly principle
Answer:
C.it contradicted the heinsberg uncertainly principle
Explanation:
Why are there multiple ways to represent molecules
Answer:
The different ways to represent compounds are chemical formulas and molecular models. There are so many ways to represent compounds so that a particular formula can be used depending upon how much information is provided and how much is needed to be share.
Explanation:
The representation of molecules depends on what property of the molecule we want to explore.
Representation of moleculesA molecule is composed of atoms of molecules. The representation of molecules depends on what property of the molecule we want to explore.
A molecule can be represented using;
Ball and stick modelSpace filling modelNewman projectionsIn each case, a particlar feature of the molecule is more vividly expressed.
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Suppose you have 300.0 mL of a 0.450 M sodium hydroxide solution.
How many moles of sodium hydroxide are in the solution?
Answer:
135 moles
Explanation:
300*0.45
= 135
PLS GIVE BRAINLIEST
3/2 moles
Explanation:We are given:
Molarity of the solution = 0.450 M
Volume of the Solution = 300 mL OR 0.3 L
Solving for the number of moles:
We know that the formula for molarity:
M = nV (where n is the number of moles and V is the volume in Liters)
replacing the variables
0.450 = n * (0.3)
n = 0.450 / 0.3
n = 3/2 moles
Therefore, we have 3/2 moles of Na(OH) in the give solution
what is Acid and any type of acid
Answer:
Acid is the substance which gives H+ ions when dissolved in an aqueous solution and tastes sour.
Types of acid
Strong acidWeak acidAnswer:
An acid is a molecule or ion capable of donating a proton (hydrogen ion H+) or, alternatively, capable of forming a covalent bond with an electron pair.
Explanation:
Hope this helped!
Which of the following elements will lose electrons to form an ion
Answer:
Metals
Explanation:
Metallic elements are renowned for their ability to freely lose electrons to form ions.
This is because metals are electropositive in nature. When a substance is electropositive, it readily wants to lose electrons and form positive ions.
Non-metals prefers to gain electrons and are electronegative.
in which beakers are the particles moving the most slowly
What would happen if you shone a lazer light into a glass of water?
Answer:
Reflection/change of direction
Explanation:
When the light of the laser hits the glass of water, it reflects and goes another direction. It's basically just a change of direction. The light is mostly in the glass of water and just some reflecting off of it.
The nucleus of an atom is made up of which of the following combinations of particles?
Answer: Atoms of different elements are found to have different number of protons, neutrons, and electrons. To distinguish one atom from another or to classify the various atoms, a number which indicates the number of protons in the nucleus of a given atom, is assigned to the atoms of each identified element. This number is known as the atomic number of the element. The atomic numbers for some of the elements which are associated with the study of semiconductors are given in the following table.
Explanation:
Element Symbol Atomic Number
Silicon Si 14
Germanium Ge 32
Arsenic As 33
Antimony Sb 51
Indium In 49
Gallium Ga 31
Boron B 5
Answer:
[tex]\boxed {\boxed {\sf Protons \ and \ neutrons}}[/tex]
Explanation:
The atom is made up of two main parts: the nucleus and the electron cloud.
The nucleus is the center and has two subatomic particles: the protons (positive charge) and the neutrons (no/neutral charge). The nucleus as a whole has a positive charge, since the neutrons don't provide a charge.
The electron cloud surrounds the nucleus and houses the negatively charged electrons in a "cloud" of energy levels.
So, the nucleus of the atom is made up of protons and neutrons.
How can energy from the Sun be used to heat water? What
things will affect how well the sunlight heats water?
Answer:
Water is heated as it travels through flat, glazed panels known as solar collectors, which are normally situated on the roof of the building. The heated water is then stored in an insulated storage tank.
1. Is it possible to distinguish DNA and RNA structures by using Bial’s Test? Explain.
2. What are the functions of orcinol and FeCl3 in Bial’s Test.
Answer:
yes and thats all i know
Explanation:
Thisssss plzzzzzzzzzzzzzzzz
6. Choose the best answer.
The definition of consecutive is:
to get in the way of; to try to prevent
facts and information
telling the meaning of
a condition of being complicated; having many parts
following one after another
Answer:
to get in the way of;to try to prevent facts and information
Plz what’s the answer to this
Answer: E
Explanation:hope this helps you out
will give branliest
How many grams of liquid water are produced when 60 grams of ice melt? Explain why.
60 Grams are produced due to the fact that it may not produce more due to the certain capacity that varies on the size of the cube.
Calculate the concentration of sulfate in a solution made from 65.0 mL of 0.55 M sodium sulfate and 85.0 mL of 1.25 M iron(III) sulfate?
we are given the molarity and the volume of solution. The only issue is that the volume is given in mL instead of L. This issue can be fixed by using the following conversion factor:
a
a
a
a
a
a
a
a
a
a
a
a
a
a
a
a
a
a
a
a
a
1000
m
L
=
1
L
Therefore, if we divide 50mL by 1000mL we will obtain a value of 0.05L.
Next, the equation has to be rearranged to solve for the moles of solute:
Moles of solute = Molarity
×
Liters of solution
Now, multiply 0.360 M by 0.05:
0.360 mol
1 L
×
0.05 L
=
0.018 mol
To obtain the mass of solute, we will need to the molar mass of NaCl, which is 58.44 g/mol:
Finally, multiply the number of moles by 58.44 g/mol
0.018
mol
×
58.44
g
1
mol
Boom, here it is:
1.05
g
When 50.0 mL of 0.400 M Ca(NO3)2 is added to 50.0 mL of 0.800 M NaF, CaF2 precipitates, as shown in the netionic equation below. The initial temperature of both solutions is 23.0°C. Assuming that the reaction goes tocompletion, and that the resulting solution has a mass of 100.00 g and a specific heat of 4.18 J/(g ∙°C), calculatethe final temperature of the solution.Ca2+(aq) + 2 F-(aq) → CaF2(s)∆H°=-11.5 kJ
Answer:
23.55°C
Explanation:
Based on the equation:
Ca²⁺(aq) + 2F⁻(aq) → CaF₂(s) ∆H°=-11.5 kJ
When 1 mole of Ca²⁺ and 2 of F⁻ reacts, 11.5kJ are released.
Thus, we need to find moles of reaction to find the heat released and using:
C = SₓmₓΔT
We can find the final temperature as follows:
Moles of reaction:
0.0500L * (0.400mol / L) = 0.0200moles Ca²⁺ = Moles of reaction
Heat produced is:
0.0200 moles * (11.5kJ / mol) = 0.23kJ
Using:
C = SₓmₓΔT
Where C is heat = 230J
S is specific heat = 4.18J/g
m is mass of solution = 100.00g
And ΔT is change in temperature
230J = 4.18J/gₓ100.00gₓΔT
ΔT = 0.55°C
As initial temperature is 23.0°C
Final temperature = 23.0°C + 0.55°C =
23.55°CThe final temperature of the solution is 23.55°C.
We were given the equation
Ca²⁺(aq) + 2F⁻(aq) → CaF₂(s) ∆H°=-11.5 kJ
This means that 1 mole of Ca²⁺ and 2 of F⁻ reacts to form CaF₂ and 1.5kJ is released.
The formula we need to use is C = SₓmₓΔT
where c is heat, s is specific heat, m is number of mole and ΔT is temperature change.
We need to find the moles of reaction first
Moles of reaction = 0.0500L × (0.400mol / L) = 0.0200moles Ca²⁺
Heat produced = 0.0200 moles ×11.5kJ / mol = 0.23kJ
We can then substitute into the formula
C = SₓmₓΔT
C = 230J
S = 4.18J/g
m = 100.00g
ΔT= ?
230J = 4.18J/gₓ100.00gₓΔT
= 0.55°C
Since the initial temperature is 23.0°C
The Final temperature will be 23.0°C + 0.55°C
=23.55°C
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A gas sample in a balloon contains 4.0 moles of gas at a particular pressure, volume and temperature. If your balloon springs a leak and the volume decreases to 1/2 of the original amount before you can plug the leak, how many moles of gas have you lost (temperature and pressure remain the same)?
Answer:
Explanation:
When volume of gas is V , pressure is P and temperature is T , if n be number of moles of gas
PV / RT = n , R is universal gas constant .
When volume becomes .5 V , pressure P and temperature T
number of moles = Px .5 V / RT = .5 PV / RT = .5 n
Number of moles of gas becomes half .
so 4 moles becomes 2 moles
No of moles lost = 4 - 2 = 2 moles.
Which order system shows the levels of organization from largest to smallest
organism, organ system cell organ tissue
organism tissue organ system organ cell
organism organ organ system cell tissue
organism organ system organ tissue cell
Answer:
3) organism organ system organ tissue cell
Explanation:
How do generators use magnets to create electricity
Answer:The properties of magnets are used to make electricity.
Explanation: Moving a magnet around a coil of wire, or moving a coil of wire around a magnet, pushes the electrons in the wire and creates an electrical current. Electricity generators essentially convert kinetic energy (the energy of motion) into electrical energy.
Bond Energy
Using the table calculate the overall energy change for this reaction.
1. How much energy is needed for bond breaking?
2. How much energy is needed for bond making?
3. What is the overall energy change? (overall energy change = reactants - products)#
4. Can you create an energy level diagram to represent this reaction?
H H
H-CEC-H
- H-C-C-H
11
+
2H-H
HH
Prom the table of the values of bond enthalpy, the values we need are:
Bond
Enthalpy (kJ/mol
H-H
432
Сас
239
CH
413
c-c
347
The magnitude of one Kelvin, one Celsius degree, and one degree on the absolute temperature scale is the same. true or false . please explain it .....
Answer:
false
Explanation:
I don't think centigrade ranges from 0 to 100 and kelvin 237 and 373 absolute -273°c and 0K
Answer:
false............................
An unknown piece of metal weighing 95.0 g is heated to 98.0°C. It is dropped into 250.0 g of water at 23.0°C. When equilibrium is reached, the temperature of the water and piece of metal is 29.0°C. Determine the specific heat of the metal. Assume the heat capacity of the container, a styrofoam cup, is negligible.
Answer:
[tex]C_{metal}=126.6\frac{J}{g\°C}[/tex]
Explanation:
Hello!
In this case, when two substances at different temperature are put in contact and an equilibrium temperature is attained, we can evidence that the heat lost by the hot substance (metal) is gained by the cold substance (water) and we can write:
[tex]Q_{metal}=-Q_{water}[/tex]
Which can be also written as:
[tex]m_{metal}C_{metal}(T_{EQ}-T_{metal})=-m_{water}C_{water}(T_{EQ}-T_{water})[/tex]
Thus, since we need the specific heat of the metal, we solve for it as shown below:
[tex]C_{metal}=\frac{m_{water}C_{water}(T_{EQ}-T_{water})}{-m_{metal}(T_{EQ}-T_{metal})} \\\\C_{metal}=\frac{250.0g*4.184\frac{J}{g\°C}(29.0\°C-98.0\°C)}{95.0g(29.0\°C-23.0\°C)} \\\\C_{metal}=126.6\frac{J}{g\°C}[/tex]
Best regards.
Is there anyone studying a doctor in pharmacy?
Answer:
no I am in 8 standard
I am already preparing for a doctor for my future
11
Which statement correctly describes both gases and liquids?"
Answer:
what are the statments?
Explanation:
A drug suspension decomposes by zero-order kinetics with a rate constant of 2 mg mL-1month-1. If the initial concentration is 100 mg mL-1, what is the shelf life (t10%)?
Answer: 5 months
Explanation: Rate Law for a reaction is an equation relating the reaction rate of reactants. It is expressed as:
aA + bB → cC + dD
[tex]r=k[A]^{a}[B]^{b}[/tex]
in which k is the rate constant of the reaction
Zero-order Kinetics is a chemical reaction in which the rate doesn't change with the variations in concentration of the reactants. At this state, it is possible to determine the final concentration by using:
[tex][A]=-kt+[A_{0}][/tex]
Shelf-Life is the time required for 10% of a drug or material to desintegrate: it is the time necessary for A to desintegrate 90% of its original concentration.
Then, the shelf-life for the drug is
[tex][A]=-kt+[A_{0}][/tex]
[tex]90=-2t+100[/tex]
2t = 10
t = 5
Shelf-life for a drug which decomposes by zero-order kinetics with rate constant of 3mgmL^{-1}month^{-1} is 5 months
The shelf life for a drug suspension decomposes by zero-order kinetics with a rate constant of 2 mg mL-1month-1 is 5 months.
How we calculate the shelf life?Shelf life for the zero order reaction will be calculated by using the below equation as:
[A] = -kt + [A₀], where
[A₀] = initial concentration of drug suspension = 100 mg/mL
[A] = Final concentration of drug suspension after 10% decomposition = 100-10 = 90mg/mol
k = rate constant = 2 mg/mL.month
t = shelf lime = to find?
On putting all these values on the above equation we get
90 = -2×t + 100
t = 10/2 = 5 months
Hence, 5 months is the shelf life.
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