Q: Which of the following is the correct formula for calculating molarity ($M$)?

$M = \dfrac{\text{moles of solute}}{\text{liters of solution}}$

Question 1

Which of the following best describes the Law of Conservation of Matter as it applies to chemical reactions?

Accepted Answer

The total mass of reactants must equal the total mass of products in a chemical reaction.

Question 2

Given the unbalanced equation $\mathrm{C_3H_8 + O_2 \rightarrow CO_2 + H_2O}$, what are the correct coefficients to balance the equation?

Accepted Answer

$1, 5, 3, 4$

Question 3

Which of the following statements about balancing chemical equations is correct?

Accepted Answer

Only coefficients in front of formulas can be changed to balance the equation.

Question 4

A sample contains $0.400$ moles of $\mathrm{N_2}$. What is the mass in grams of this sample? (Molar mass of $\mathrm{N_2} = 28.0\ \mathrm{g/mol}$)

Accepted Answer

$11.2\ \mathrm{g}$

Question 5

How many moles of $\mathrm{Na}$ are present in a $62.8\ \mathrm{g}$ sample of sodium metal? (Molar mass of $\mathrm{Na} = 23.0\ \mathrm{g/mol}$)

Accepted Answer

$2.73\ \mathrm{mol}$

Question 6

If $10.0\ \mathrm{g}$ of carbon reacts with excess oxygen to form carbon dioxide, what mass of $\mathrm{O_2}$ is required? (Molar mass: $\mathrm{C} = 12.0\ \mathrm{g/mol}$, $\mathrm{O_2} = 32.0\ \mathrm{g/mol}$)

Accepted Answer

$22.2\ \mathrm{g}$

Question 7

A solution is prepared by dissolving $3.50\ \mathrm{mol}$ of $\mathrm{NaCl}$ in enough water to make $2.00\ \mathrm{L}$ of solution. What is the molarity of the solution?

Accepted Answer

$1.75\ \mathrm{M}$

Question 8

What is the molarity of a solution containing $18.23\ \mathrm{g}$ of $\mathrm{HCl}$ dissolved in $2.0\ \mathrm{L}$ of solution? (Molar mass of $\mathrm{HCl} = 36.46\ \mathrm{g/mol}$)

Accepted Answer

$0.500\ \mathrm{M}$

Question 9

How many liters of $12.0\ \mathrm{M}$ HCl solution are needed to obtain $0.425\ \mathrm{mol}$ of HCl?

Accepted Answer

$0.0354\ \mathrm{L}$

Question 10

A saline solution is $0.15\ \mathrm{M}$ NaCl. What mass of NaCl is required to prepare $0.50\ \mathrm{L}$ of this solution? (Molar mass of NaCl = $58.4\ \mathrm{g/mol}$)

Accepted Answer

$4.38\ \mathrm{g}$

Question 11

Which of the following best describes a solution?

Accepted Answer

A homogeneous mixture of two or more substances.

Question 12

What is the percent by mass of NaCl in a solution made by dissolving $25.5\ \mathrm{g}$ NaCl in $425\ \mathrm{g}$ of water?

Accepted Answer

$5.66\%$

Question 13

If $120\ \mathrm{mL}$ of oil is dissolved in enough gasoline to make $4,000\ \mathrm{mL}$ of solution, what is the percent by volume of oil in the mixture?

Accepted Answer

$3.0\%$

Question 14

Which of the following is the correct formula for calculating molarity ($M$)?

Accepted Answer

$M = \dfrac{	ext{moles of solute}}{	ext{liters of solution}}$

Question 15

A reaction is carried out with $0.105\ \mathrm{mol}$ of propane ($\mathrm{C_3H_8}$) in excess oxygen. How many moles of $\mathrm{O_2}$ are consumed? ($\mathrm{C_3H_8 + 5O_2 \rightarrow 3CO_2 + 4H_2O}$)

Accepted Answer

$0.525\ \mathrm{mol}$

Question 16

Which of the following is Avogadro's number?

Accepted Answer

$6.02 	imes 10^{23}$

Question 17

What is the formula mass of $\mathrm{(NH_4)_2SO_4}$? (Atomic masses: N = $14.0\ \mathrm{u}$, H = $1.01\ \mathrm{u}$, S = $32.0\ \mathrm{u}$, O = $16.0\ \mathrm{u}$)

Accepted Answer

$132.1\ \mathrm{u}$

Question 18

Which of the following best describes a solute?

Accepted Answer

The substance being dissolved in a solution.

Question 19

A solution is made by dissolving $333\ \mathrm{g}$ of $\mathrm{KHCO_3}$ in enough water to make $10.0\ \mathrm{L}$ of solution. What is the molarity of the solution? (Molar mass of $\mathrm{KHCO_3} = 100.1\ \mathrm{g/mol}$)

Accepted Answer

$0.333\ \mathrm{M}$

Chapter 5: Chemical Accounting – Study Notes for CHEM 110

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