Q: A sample contains 10 g of nickel (Ni). Given the molar mass of Ni is 58.69 g/mol, how many Ni atoms are present in the sample?

$$1.0 \times 10$$^{23}$$ Ni atoms

Q: A 5 mL sample of liquid bromine ($$Br_2) $$has a density of 3.1 g/mL. How many bromine atoms are present in the sample? (Molar mass $$Br_2 = 159.81 g/$$mol)

$$1.2 \times 10$$^{23}$$ Br atoms

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

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

Question 1

A sample contains 10 g of nickel (Ni). Given the molar mass of Ni is 58.69 g/mol, how many Ni atoms are present in the sample?

Accepted Answer

$$1.0 	imes 10$$^{23}$$ Ni atoms

Question 2

What is the percent by mass of potassium in $$K_2SO_4$$? (Atomic masses: K = 39.10 g/mol, S = 32.06 g/mol, O = 16.00 g/mol)

Accepted Answer

$$44.9\%$$

Question 3

A 5 mL sample of liquid bromine ($$Br_2) $$has a density of 3.1 g/mL. How many bromine atoms are present in the sample? (Molar mass $$Br_2 = 159.81 g/$$mol)

Accepted Answer

$$1.2 	imes 10$$^{23}$$ Br atoms

Question 4

Given two isotopes of bromine: $$^{79}Br (78.92 $$amu, 50.69%) and $$^{81}Br (80.92 $$amu, 49.31%), what is the average atomic mass of bromine?

Accepted Answer

$$79.91$$ amu

Question 5

Which of the following is the correct name for $$Mg(OH)_2$$?

Accepted Answer

Magnesium hydroxide

Question 6

Balance the following chemical equation: $$C_4H_{10}(g) + O_2$(g) \rightarrow CO_2$(g) + H_2O(g). $$What are the correct coefficients?

Accepted Answer

$$2C_4H_{10} + 13O_2 \rightarrow 8CO_2 + 10H_2O$$

Question 7

In the reaction $$2H_2(g) + O_2$(g) \rightarrow 2H_2O(g)$$, if you start with 10 molecules of $$H_2$$ and 7 molecules of $$O_2$$, what is the limiting reactant and how many molecules of $$H_2O$$ are formed?

Accepted Answer

$$H_2 is $$limiting; 10 molecules of $$H_2O$$ are formed

Question 8

A mixture contains 5 molecules of $$CH_4$$ and 8 molecules of $$O_2. $$For the reaction $$CH_4 + 2O_2$$ \rightarrow $$CO_2 + 2H_2O$, what is the limiting reactant and the theoretical yield of CO_2$ molecules?

Accepted Answer

$$O_2 is $$limiting; 4 molecules of $$CO_2$$ are formed

Question 9

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

Accepted Answer

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

Question 10

If the theoretical yield of nitrogen gas from a reaction is 8.0 g, but only 7.0 g is actually produced, what is the percent yield?

Accepted Answer

$$87.5\%$$

Question 11

Which statement best describes the role of coefficients in a balanced chemical equation?

Accepted Answer

They indicate the ratio of moles of reactants and products involved in the reaction.

Question 12

In the reaction $$2Mg(OH)_2(s) + 4HCl(aq) \rightarrow 4H_2O(l) + 2MgCl_2(aq)$$, how many grams of HCl are neutralized by 3.26 g of $$Mg(OH)_2$$? (Molar mass $$Mg(OH)_2 = 58.32 g/$$mol, HCl = 36.46 g/mol)

Accepted Answer

$$4.08 g $$HCl

Question 13

During the combustion of octane ($$C_8H_{18}$$), how many grams of $$CO_2$$ are produced from the combustion of $$4.0 	imes 10^5$ g of gasoline? (Molar mass C_8H$$_{18}$$ = 114.26 g/mol, CO_2$ = 44.01 g/mol, 2C_8H$$_{18} + 25O_2 ightarrow 16CO_2 + 18H_2O$$)

Accepted Answer

$$1.2 	imes 10^6$ g CO_2$

Question 14

Which of the following is the correct name for $$FeSO_4$$?

Accepted Answer

Iron(II) sulfate

Question 15

What is the correct name for $$P_2O_3$$?

Accepted Answer

Diphosphorus trioxide

Question 16

Which of the following acids is formed when $$HNO_3 is $$dissolved in water?

Accepted Answer

Nitric acid

Question 17

A power plant produces 25 kg of $$SO_2$$ per year. Assuming excess $$O_2$$ and $$H_2O$$, what mass of $$H_2SO_4 (in kg) $$can be formed? ($$2SO_2 + O_2$ + 2H_2O \rightarrow 2H_2SO_4$$, molar mass $$SO_2 = 64.07 g/$$mol, $$H_2SO_4 = 98.09 g/$$mol)

Accepted Answer

$$38.3 kg$$ $$H_2SO_4$$

Question 18

In photosynthesis, plants convert $$CO_2$$ and $$H_2O to $$glucose ($$C_6H_{12}O_6$) and O_2$. If a plant consumes 37.8 g of CO_2$, what mass of glucose can be synthesized? (Molar mass CO_2$ = 44.01 g/mol, C_6H$$_{12}$$O_6 = 180.16 g/$$mol, $$6CO_2 + 6H_2O \rightarrow C_6H_{12}O_6$ + 6O_2)$$

Accepted Answer

$$25.9 g $$glucose

General Chemistry I: Chemical Reactions and Problem Solving (Lecture 9, Chapter 4)

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