Q: Which of the following is the correct formula for calculating percent yield?

$$\frac{\text{actual yield (g)}}{\text{theoretical yield (g)}} \times 100\%$$

Q: How many oxygen atoms are present in 0.150 mole of aspirin ($$\mathrm{C_9H_8O_4}$$)?

$$0.150 \times 4 \times 6.02 \times 10$$^{23}$$

Q: If 7.54 g of calcium oxide is obtained from the decomposition of 16.0 g of calcium carbonate ($$\mathrm{$$CaCO_3$$}$$), what is the percent yield?

$$\frac{7.54}{8.96} \times 100\%$$

Q: How many molecules are contained in 5.0 moles of carbon dioxide ($$\mathrm{CO_2$}$$)?

$$5.0 \times 6.02 \times 10$$^{23}$$

Question 1

Which of the following best describes the chemical change shown in the image of the tarnishing of silver (Ag) to form silver sulfide (Ag2S)?

Accepted Answer

A combination reaction, because two elements combine to form a compound.

Question 2

In the chemical equation $$\mathrm{CH_4$ + 2\ O_2$ \rightarrow CO_2$ + 2\ H_2O}$$, what do the coefficients represent?

Accepted Answer

The number of molecules or moles of each substance involved in the reaction.

Question 3

Which type of reaction is illustrated by the diagram where two reactants (A and B) combine to form one product (AB)?

Accepted Answer

Combination reaction

Question 4

Given the reaction $$\mathrm{2\ NH_3$ \rightarrow N_2$ + 3\ H_2$}$$, what type of reaction is this?

Accepted Answer

Decomposition reaction

Question 5

Which of the following is the correct formula for calculating percent yield?

Accepted Answer

$$\frac{	ext{actual yield (g)}}{	ext{theoretical yield (g)}} 	imes 100\%$$

Question 6

How many oxygen atoms are present in 0.150 mole of aspirin ($$\mathrm{C_9H_8O_4}$$)?

Accepted Answer

$$0.150 	imes 4 	imes 6.02 	imes 10$$^{23}$$

Question 7

A student reacts 48.0 g of methanol ($$\mathrm{CH_3OH}$$, molar mass = 32.04 g/mol) with excess oxygen. What is the theoretical yield of water ($$\mathrm{H_2O}$$, molar mass = 18.02 g/mol) produced according to the equation $$2\ \mathrm{CH_3OH} + 3\ \mathrm{O_2$} \rightarrow 2\ \mathrm{CO_2$} + 4\ \mathrm{H_2O}$$?

Accepted Answer

54.0 g

Question 8

Which of the following statements about limiting reactants is TRUE?

Accepted Answer

The limiting reactant determines the maximum amount of product that can be formed.

Question 9

If 7.54 g of calcium oxide is obtained from the decomposition of 16.0 g of calcium carbonate ($$\mathrm{$$CaCO_3$$}$$), what is the percent yield?

Accepted Answer

$$\frac{7.54}{8.96} 	imes 100\%$$

Question 10

Which of the following is NOT a sign that a chemical reaction has occurred?

Accepted Answer

Melting of a solid

Question 11

How many molecules are contained in 5.0 moles of carbon dioxide ($$\mathrm{CO_2$}$$)?

Accepted Answer

$$5.0 	imes 6.02 	imes 10$$^{23}$$

Question 12

Which reaction type is illustrated by the equation $$\mathrm{Zn(s) + 2HCl(aq) \rightarrow $$ZnCl_2$$(aq) + H_2$(g)}$$?

Accepted Answer

Single replacement reaction

Question 13

What is the molar mass of ammonium phosphate ($$\mathrm{(NH_4$)_3PO_4}$$)?

Accepted Answer

149.10 g/mol

Question 14

A student wants to calculate the mass of 8.7 $$	imes$$ $$10^{25}$$ molecules of glycine ($$\mathrm{C_2H_5NO_2}$$, molar mass = 75.07 g/mol). Which conversion factors should they use?

Accepted Answer

Avogadro's number and molar mass

Question 15

In a reaction, 32.5 g of ammonia ($$\mathrm{NH_3$}) $$and 42.65 g of oxygen ($$\mathrm{O_2$}) $$are mixed. How do you determine which is the limiting reactant?

Accepted Answer

Convert both masses to moles of product and compare; the smaller value is the limiting reactant.

Question 16

Which of the following is a double replacement reaction?

Accepted Answer

$$\mathrm{ZnS(s) + 2HCl(aq) \rightarrow $$ZnCl_2$$(aq) + H_2S(g)}$$

Question 17

Which equation correctly relates grams, moles, and molecules for a substance?

Accepted Answer

$$	ext{grams} ightarrow 	ext{moles} ightarrow 	ext{molecules}$$

Question 18

Which of the following is NOT a reason why actual yield is less than theoretical yield?

Accepted Answer

Perfect experimental technique

Chemical Reactions: Types, Calculations, and Stoichiometry

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