Q: What is the formula for molarity ($M$)?

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

Question 1

Which statement best describes the purpose of a balanced chemical equation?

Accepted Answer

It shows the exact relationship between the amounts of reactants and products in moles.

Question 2

Octane ($\mathrm{C_8H_{18}}$) combusts according to the equation: $2\mathrm{C_8H_{18}}(l) + 25\mathrm{O_2}(g) \rightarrow 16\mathrm{CO_2}(g) + 18\mathrm{H_2O}(g)$. If a 50.0 L gas tank contains 300. moles of octane, how many moles of $\mathrm{CO_2}$ are produced when all the octane is burned?

Accepted Answer

$2400 	ext{ moles}$

Question 3

During photosynthesis, the reaction $6\mathrm{CO_2}(g) + 6\mathrm{H_2O}(l) \xrightarrow{sunlight} 6\mathrm{O_2}(g) + \mathrm{C_6H_{12}O_6}(aq)$ occurs. If a plant consumes 37.8 g of $\mathrm{CO_2}$, what mass of glucose ($\mathrm{C_6H_{12}O_6}$) can be synthesized?

Accepted Answer

$25.8 	ext{ g}$

Question 4

A medium-sized home produces 16.0 kg of $\mathrm{NO_2}$ annually. Given the reaction $4\mathrm{NO_2}(g) + \mathrm{O_2}(g) + 2\mathrm{H_2O}(l) \rightarrow 4\mathrm{HNO_3}(aq)$, what mass of $\mathrm{HNO_3}$ is formed from this release of $\mathrm{NO_2}$?

Accepted Answer

$21.9 	ext{ kg}$

Question 5

In the reaction $4\mathrm{Na}(s) + \mathrm{O_2}(g) \rightarrow 2\mathrm{Na_2O}(s)$, if a flask contains 3 molecules of $\mathrm{O_2}$, how many sodium atoms are required to react with all the oxygen?

Accepted Answer

12 sodium atoms

Question 6

You have 6 graham crackers, 3 marshmallows, and 4 chocolate squares. According to the s'mores 'reaction' (1 graham cracker + 1 marshmallow + 1 chocolate square $\rightarrow$ 1 s'more), which ingredient is the limiting reactant?

Accepted Answer

Marshmallows

Question 7

Given the s'mores 'reaction' (1 graham cracker + 1 marshmallow + 1 chocolate square $\rightarrow$ 1 s'more), how many s'mores can you make with 6 graham crackers, 3 marshmallows, and 4 chocolate squares?

Accepted Answer

3

Question 8

For the reaction $\mathrm{N_2}(g) + 3\mathrm{H_2}(g) \rightarrow 2\mathrm{NH_3}(g)$, if a flask initially contains 2 molecules of $\mathrm{N_2}$ and 6 molecules of $\mathrm{H_2}$, what will be present after the reaction is complete?

Accepted Answer

4 molecules of $\mathrm{NH_3}$, no $\mathrm{N_2}$ or $\mathrm{H_2}$ left

Question 9

Magnesium reacts with oxygen: $2\mathrm{Mg}(s) + \mathrm{O_2}(g) \rightarrow 2\mathrm{MgO}(s)$. If a mixture contains 42.5 g Mg and 33.8 g $\mathrm{O_2}$, what is the limiting reagent?

Accepted Answer

$\mathrm{Mg}$

Question 10

Using the previous reaction ($2\mathrm{Mg}(s) + \mathrm{O_2}(g) \rightarrow 2\mathrm{MgO}(s)$), what is the theoretical yield of $\mathrm{MgO}$ in grams if the limiting reagent is 42.5 g Mg?

Accepted Answer

$69.9 	ext{ g}$

Question 11

If the actual yield of $\mathrm{MgO}$ in the previous reaction is 55.9 g, what is the percent yield?

Accepted Answer

$80.0\%$

Question 12

For the reaction $3\mathrm{NO_2}(g) + \mathrm{H_2O}(l) \rightarrow 2\mathrm{HNO_3}(l) + \mathrm{NO}(g)$, if 5 moles of $\mathrm{NO_2}$ react with 1 mole of water, how many moles of the excess reagent remain after the reaction?

Accepted Answer

2 mol

Question 13

Which of the following best defines a solution in chemistry?

Accepted Answer

A homogeneous mixture of two or more pure substances

Question 14

Which statement correctly describes a concentrated solution?

Accepted Answer

It contains a large quantity of solute relative to the amount of solvent.

Question 15

What is the formula for molarity ($M$)?

Accepted Answer

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

Question 16

Which equation is used to calculate the dilution of solutions?

Accepted Answer

$M_1V_1 = M_2V_2$

Question 17

Molality ($m$) is defined as:

Accepted Answer

Moles of solute per kilogram of solvent

Question 18

How many liters of a $0.125\ \mathrm{mol\ L^{-1}}$ NaOH solution contains $0.255$ mol NaOH?

Accepted Answer

$2.04\ \mathrm{L}$

Question 19

To what volume should you dilute $0.200\ \mathrm{L}$ of a $15.0\ \mathrm{M}$ NaOH solution to obtain a $3.00\ \mathrm{M}$ NaOH solution?

Accepted Answer

$1.00\ \mathrm{L}$

Question 20

What volume of a $0.150\ \mathrm{M}$ KCl solution will completely react with $0.150\ \mathrm{L}$ of a $0.175\ \mathrm{M}$ Pb(NO$_3$)$_2$ solution according to the reaction $2\mathrm{KCl}(aq) + \mathrm{Pb(NO_3)_2}(aq) \rightarrow \mathrm{PbCl_2}(s) + 2\mathrm{KNO_3}(aq)$?

Accepted Answer

$0.350\ \mathrm{L}$

Chapter 4 – Reaction Stoichiometry & Solution Chemistry: Study Notes

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