Answer this question correctly and you'll get a free brainliest. and a Thank you, etc.

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.

Answer:

Just count all the different elements like what elemets are in there and you have to identify the number of elemenst

Explanation:

for example H20 and a chemical for example thats two so you identofy which elelments are in there doesnt matter if thered multiple of it all its asking is what id the number of elemts there meaning like one or 2 mayne six different elements

Answer:

They are plants also known as plankton and they produce about 80-85% of the world's oxygen.

Explanation:

Answer:

Ans: 541 mmHg

Explanation:

given:

H2 = 31mmHg

CO= 510mmHg

get the sum

31+510=541

Answer:

Explanation:

The chemical expression for the reaction between iron and oxygen is:

4Fe(s)  +  3O₂ (g)  [tex]\to[/tex] 2Fe₂O₃ (s)

The number of moles of Fe = mass of Fe/ molecular mass of Fe

The number of moles of Fe = 56 g/ 55.845 g/mol

The number of moles of Fe = 1.002 moles of Fe

The number of moles of oxygen = mass of oxygen/ molecular mass of oxygen

The number of moles of oxygen = 156 g /32 g/mol

The number of moles of oxygen = 4.875 moles of oxygen

Assume that Fe is the limiting reactant, the number of Fe₂O₃ can be calculated as:

moles of Fe₂O₃ = 1.002 mole of Fe × 2 moles of Fe₂O₃/ 4 moles of Fe

moles of Fe₂O₃ = 0.501 mole of Fe₂O₃

Assume that O₂ is the limiting factor, the number of Fe₂O₃ is:

moles of Fe₂O₃ = 4.875 moles of O₂ × 2 moles of Fe₂O₃/ 3 moles of O₂

moles of Fe₂O₃ = 3.25 mole of Fe₂O₃

Thus, after the reaction is complete, Fe and O₂ contain different moles of Fe₂O₃. Only Fe gets consumed in the reaction and it is the limiting factor.

Answer:

answer d is correct that works

Answer:

20 ml

Explanation:

Answer:

its c on edge 2021

Explanation:

During phase change, kinetic energy does not change, but the potential energy does. Therefore, the correct option is option C among all the given options.

Kinetic energy is a type of power that a moving object or particle possesses. An item accumulates kinetic energy when work, which involves the transfer of energy, being done on it by exerting a net force. A moving object and particle has kinetic energy, which relies on both its mass and its rate of motion.

This formula only works for particles traveling at low to moderate speeds; for particles traveling at extremely high speeds, it produces results that are too low. The rules of relativity must be applied when an object's speed approaches the speed of light (3 108 meters per second, about 186,000 miles per second). During phase change, kinetic energy does not change, but the potential energy does.

Therefore, the correct option is option C among all the given options.

To learn more about kinetic energy, here:

https://brainly.com/question/11592500

#SPJ6

Answer:

Evaporation is a technique used to separate out homogeneous mixtures where there is one or more dissolved salts.

Explanation:

Hope this helps :)

Explanation:

The pressure will decrease but the volume remains constant

Answer:

0.1 g/dl

Explanation:

The standard curve is a graph that relates the absorbance at 400 nm with the concentration of haemoglobin in mg/dl. To obtain the concentration from the absorbance value, we enter in the x-axis (absorbance at 400 nm) with the value 0.40 (the line between 0.2 and 0.6), we extrapolate the line to the curve and read the correspondent value on y-axis (concentration in mg/dl): 100 mg/dl.

So, we convert the concentration from mg/dl to g/dl by dividing into 1000:

100 mg/dl x 1 g/1000 mg = 0.1 g/dl

Therefore, the concentration of haemoglobin of the patient is 0.1 g/dl.

Answer:

The total mass of the solution = 99.7 g

Note: The question is incomplete. The complete question is given below:

A "coffee-cup" calorimetry experiment is run for the dissolution of 2.5 g of lithium nitrate placed into 97.2 mL of water. The temperature of the solution is initially at 23.5oC. After the reaction takes place, the temperature of the solution is 28.3 oC.  

1. Using a density of 1.0 g/mL for the water added and adding in the mass of the lithium nitrate, what is the total mass of the solution and solid?

Explanation:

mass = density * volume

density of water = 1.0 g/mL; volume of water = 97.2 mL

mass of water = 1.0 g/L * 97.2 mL

mass of water = 97.2 g

mass of lithium nitrate = 2.5 g

A solution is made by dissolving a solute (usually solid) in a solvent (usually a liquid). The solute in this reaction is lithium nitrate and the solvent is water.

Total mass of solution = mass of water + mass of lithium nitrate

Total mass of solution = 97.2 g + 2.5 g = 99.7 g

Therefore, total mass of the solution = 99.7 g

The total mass of the solution of lithium nitrate solution has been 99.7 grams.

Density can be defined as the mass of the solute per unit volume. The density can be expressed as g/ml or kg/L.

The mass of given Lithium nitrate = 2.5 grams.

The mass of water can be given as:

Density = [tex]\rm \dfrac{Mass}{Volume}[/tex]

Volume of water = 97.2 ml.

The total mass of solution:

Mass of water = Density [tex]\times[/tex] Volume

Mass of water = 1 [tex]\times[/tex] 97.2 grams

Mass of water = 97.2 grams

The total mass = Mass of lithium nitrate + mass of water

= 2.5 + 97.2 grams

= 99.7 grams.

The total mass of the solution of lithium nitrate solution has been 99.7 grams.

For more information about density, refer to the link:

https://brainly.com/question/14940265

Answer:

Option B. Cation that is smaller than the original atom.

Explanation:

Magnesium is a divalent element. This implies that magnesium can give up 2 electrons to become an ion (cation) as shown below:

Mg —> Mg²⁺ + 2e¯

Next, we shall write the electronic configuration of magnesium atom (Mg) and magnesium ion (Mg²⁺). This can be written as follow:

Mg (12) = 2, 8, 2

Mg²⁺ (10) = 2, 8

From the above illustration, we can see that the magnesium atom (Mg) has 3 shells while the magnesium ion (Mg²⁺) has 2 shells.

This simply means that the magnesium ion (Mg²⁺) i.e cation is smaller that the original magnesium atom (Mg).

Answer:

39.1-32.5 and you will find your answer it always like that, you subtract your starting point from your ending point

Explanation:

The volume of the piece of lead is 6.6 mL

From the question given above, the following data were obtained:

The volume of the lead can be obtained as follow:

Volume of lead = (Volume of water + Lead) – (Volume of water)

Volume of lead = 39.1 – 32.5

Volume of lead = 6.6 mL

Therefore the volume of the lead is 6.6 mL

Learn more about density: https://brainly.com/question/7622627

The reaction already balanced

Equalization of chemical reactions can be done using variables. Steps in equalizing the reaction equation:  

• 1. gives a coefficient on substances involved in the equation of reaction such as a, b, or c, etc.  

• 2. make an equation based on the similarity of the number of atoms where the number of atoms = coefficient × index (subscript) between reactant and product  

• 3. Select the coefficient of the substance with the most complex chemical formula equal to 1  

For gas combustion reaction which is a reaction of hydrocarbons with oxygen produces CO₂ and H₂O (water vapor). can use steps:  

Balancing C, H and the last O  

Reaction

KOH (aq) + HNO₃ (aq) ⇒ KNO₃ (aq) + H₂0 (l)

aKOH (aq) + bHNO₃ (aq) ⇒ KNO₃ (aq) + cH₂0 (l)

K : left = a, right = 1⇒a=1

N : left = b, right =1, b=1

H: left = a, right a+b=2c⇒1+1=2c⇒2=2c⇒c=1

KOH (aq) + HNO₃ (aq) ⇒ KNO₃ (aq) + H₂0 (l)⇒ already balanced

Answer:

Isotopes are variants of an element, where the number of neutrons is different but its number of protons stay the same.

Explanation:

If the number of protons had changed then it would just be a different element.

Electron number changing simply adds charge to the atom, and doesn't change it or anything.

PLS GIVE BRAINLIEST

Answer:

Isotopes are one of two or more forms of the same chemical element.

Explanation:

Different isotopes of an element have the same number of protons in the nucleus, giving them the same atomic number,but a different number of neutrons giving each element isotope of a different atomic weight.

Answer:

76.366

Explanation:

Knewton answer is 76.4

Answer:

76.4mL

Explanation:

First, calculate the final number of moles of carbon dioxide (n2) in the container.

n2 = n1+n added = 3.41×(10^-3) mol+8.41×(10^-4) mol = 4.25×(10^-3) mol

Rearrange Avogadro's law to solve for V1.

V1 =(V2×n1)/n2

Substitute in the known values for n1, V2, and n2.

V1 = (95.2mL×(3.41×10^-3 mol))/(4.25×(10^-3) mol)=76.4mL

So the initial volume is 76.4mL.

Answer:

H₂O

Explanation:

Based electronegativity, water H₂O will have the higher melting point from the given choices. The binding force between hydrogen and oxygen is greater than for the others.

Answer:

H2O

Explanation:

hoffe das hilfts

Answer:

100 thousand million stars

Explanation:

Answer:

100 to 400 billion stars

Answer:

The coins will turn green faster because chemical reaction speed up with higher temperatures

Copper coins turn green when exposed to water because the coins will turn green faster because reaction speeds up with higher temperatures.

The rate of a chemical reaction can be defined as the speed at which the products are formed from the reactants. The rate of a reaction gives information about the time frame under which a reaction can be finished.

The rate of reaction can be described as the speed of a chemical reaction at which reactants are transformed into products. Some chemical reactions are generally instantaneous, while some reactions take time to reach the final equilibrium. Pressure increases the concentration of gaseous reactants resulting in an increase in the rate of reaction.

The rate of reaction will increase with an increase in the temperature of the reaction as the reactant molecules get more kinetic energy and increase the number of collisions.

Therefore, copper coins will turn green faster because reactions speed up with higher temperatures.

Learn more about the rate of reaction, here:

brainly.com/question/13571877

#SPJ2

Answer:

D

Explanation:

it is trigonal planar, because central atom does not have the lone pairs, equal repulsion

The molecular geometry of the central atom in ClO3- will be triangular pyramidal.

The geometry of molecular structures can be predicted using the chemical model known as the valence shell electron pair repulsion hypothesis based on the number of electron pairs surrounding the core atoms of the molecules.

Since ClO3- has a steric number of 4 (one unpaired pair as well as three bonded pairs), can infer that its molecular shape is triangular pyramidal. Its electrical form is tetrahedral, as shown by the Lewis structure above.

Therefore, the correct answer will be option (c).

To know more about VSEPR theory.

https://brainly.com/question/14992767

#SPJ3

Answer:

A and D

Explanation:

Answer:your a poop face

Explanation:

Imagine not knowing the answer

Answer: C

Explanation:

Answer:

i dont really know this one

Explanation:

Ions can be made by single element or covalently bonded group of elements. The covalently bonded group of elements is called polyatomic ions or polyatomic atoms.

Any species that contain charge whether it is positive charge or negative charge is called ions. The example of polyatomic ions are sulfate, phosphate, nitrate etc.

a)Electronic configuration of Be is 1s² 2s² and the common ion formed by it is Be⁺².

b)Electronic configuration of Cl is [Ne]3S² 3p⁵and the common ion formed by it is Cl⁻.

c)Electronic configuration of  Se is [Ar] 3d¹⁰ 4s² 4p⁴ and the common ion formed by it is Se⁻².

d)Electronic configuration of Rb isKr 5s¹ and the common ion formed by it is Rb⁺¹ .

Therefore, Cation is the species that loose electron and attain positive charge while anion is a species which gain electron and attains negative charge

To learn more about ions, here:

https://brainly.com/question/13692734

#SPJ5

10.86 moles of water are produced

A reaction coefficient is a number in the chemical formula of a substance involved in the reaction equation. The reaction coefficient is useful for equalizing reagents and products.

Reaction

Pb + PbO₂ + 2H₂SO₄ ⇒ 2PbSO₄ + 2H₂O ( a car battery reaction)

From the equation :

mol ratio PbO₂ : H₂O = 1 : 2⇒ 1 mol PbO₂ produces 2 mol H₂O

so for 5.43 mol PbO₂ consumed,  mol H₂O :

[tex]\tt 2\times 5.43=10.86~moles[/tex]

Answer:

10.9

Explanation:

edge 2020

Answer:

However copper ore is a finite resource and it makes sense to conserve ore by recycling. It is cheaper to recycle old copper than to mine and extract new copper.

Answer:

[tex]\boxed {\boxed {\sf 39}}[/tex]

Explanation:

The mass number of an atom can be found by adding the number of protons and neutrons.

[tex]mass \ number =protons + neutrons[/tex]

There are 19 protons and 20 neutrons.

[tex]protons=19 \\neutrons=20[/tex]

[tex]mass \ number= 19+20[/tex]

[tex]mass \ number =39[/tex]

The mass number of this atom is 39

Answer:

0.0681 HCl moles

Explanation:

First we convert 22.7 mL to liters:

Then we use the definition of molarity:

So there are 0.0681 hydrochloric acid moles in 22.7 mL of a 3.0 M HCl solution.

Answer:

1

Explanation:

because there barely eating and there eating protien and healthy foods