Q: How many molecules are present in $0.25$ moles of $CO_2$? ($Avogadro's\ number = 6.022 \times 10^{23}$)

$1.51 \times 10^{23}$ molecules

Q: Which formula is used to calculate the concentration of a solution in molarity ($M$)?

$M = \dfrac{\text{moles of solute}}{\text{volume of solution (L)}}$

Q: Which formula is used to calculate percent yield in a chemical reaction?

$\text{Percent Yield} = \dfrac{\text{Actual Yield}}{\text{Theoretical Yield}} \times 100\%$

Question 1

Which of the following best describes the difference between molecular mass and molar mass?

Accepted Answer

Molecular mass is the sum of the atomic masses of all atoms in a molecule (in amu), while molar mass is the mass of one mole of that substance (in g/mol).

Question 2

A sample contains $18.0$ grams of water ($H_2O$). How many moles of water are present in the sample? ($Molar\ mass\ of\ H_2O = 18.0\ g/mol$)

Accepted Answer

$1.0$ mole

Question 3

How many molecules are present in $0.25$ moles of $CO_2$? ($Avogadro's\ number = 6.022 	imes 10^{23}$)

Accepted Answer

$1.51 	imes 10^{23}$ molecules

Question 4

Which formula is used to calculate the concentration of a solution in molarity ($M$)?

Accepted Answer

$M = \dfrac{	ext{moles of solute}}{	ext{volume of solution (L)}}$

Question 5

A $0.50$ L solution contains $0.10$ moles of $NaCl$. What is the molarity of the solution?

Accepted Answer

$0.20\ M$

Question 6

Which of the following best illustrates the Law of Conservation of Mass in a chemical reaction?

Accepted Answer

The total mass of reactants equals the total mass of products.

Question 7

Which of the following is a balanced chemical equation for the synthesis of water from hydrogen and oxygen?

Accepted Answer

$2H_2 + O_2 \rightarrow 2H_2O$

Question 8

Which type of chemical reaction is represented by the following equation? $2KClO_3 \rightarrow 2KCl + 3O_2$

Accepted Answer

Decomposition

Question 9

Which of the following reactions is a precipitation reaction?

Accepted Answer

$AgNO_3(aq) + NaCl(aq) \rightarrow AgCl(s) + NaNO_3(aq)$

Question 10

Given the reaction $2Na + Cl_2 \rightarrow 2NaCl$, which element is oxidized and which is reduced?

Accepted Answer

Na is oxidized, Cl is reduced.

Question 11

What is the oxidation number of sulfur in $SO_2$?

Accepted Answer

$+4$

Question 12

If $3.0$ moles of $Fe$ react with $4.5$ moles of $O_2$ to produce $Fe_2O_3$ according to the equation $4Fe + 3O_2 \rightarrow 2Fe_2O_3$, how many moles of $Fe_2O_3$ are produced?

Accepted Answer

$1.5$ moles

Question 13

Which of the following best describes a double displacement reaction?

Accepted Answer

Two compounds exchange ions to form two new compounds.

Question 14

A student mixes $BaCl_2(aq)$ and $Na_2SO_4(aq)$. According to the solubility chart, $BaSO_4$ is insoluble. What will happen?

Accepted Answer

$BaSO_4$ will precipitate out of solution.

Question 15

Which formula is used to calculate percent yield in a chemical reaction?

Accepted Answer

$	ext{Percent Yield} = \dfrac{	ext{Actual Yield}}{	ext{Theoretical Yield}} 	imes 100\%$

Question 16

A reaction has a theoretical yield of $10.0$ grams, but only $7.5$ grams are actually produced. What is the percent yield?

Accepted Answer

$75\%$

Question 17

Which of the following is an example of an acid-base neutralization reaction?

Accepted Answer

$HCl(aq) + NaOH(aq) \rightarrow NaCl(aq) + H_2O(l)$

Question 18

How many grams of $Na_2SO_4$ are needed to prepare $0.25$ moles? ($Molar\ mass\ of\ Na_2SO_4 = 142\ g/mol$)

Accepted Answer

$35.5$ grams

Question 19

Which of the following best describes a redox reaction?

Accepted Answer

A reaction in which electrons are transferred between species.

General Chemistry Study Guide: Mole Calculations, Chemical Reactions, and Solution Chemistry

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