Q: Which of the following is the correct formula weight (FW) calculation for calcium chloride ($$\mathrm{$$CaCl_2$$}$$)?

$$1 \times 40.08\ \mathrm{amu} + 2 \times 35.453\ \mathrm{amu} = 110.99\ \mathrm{amu}$$

Q: Which of the following statements about the mole is correct?

One mole of any substance contains $$6.02214 \times 10$$^{23}$$ particles.

Question 1

Which of the following best describes why coefficients, rather than subscripts, are changed when balancing chemical equations?

Accepted Answer

Changing coefficients changes the amount of substances, while changing subscripts changes the identity and properties of the compounds.

Question 2

A precisely machined sphere of $$^{28}\mathrm{Si}$$ was used to redefine which fundamental constant?

Accepted Answer

Avogadro's number

Question 3

What is the balanced chemical equation for the complete combustion of pentane ($$\mathrm{C_5H_{12}}$$)?

Accepted Answer

$$\mathrm{C_5H_{12} + 8O_2 \rightarrow 5CO_2 + 6H_2O}$$

Question 4

Which of the following is the correct formula weight (FW) calculation for calcium chloride ($$\mathrm{$$CaCl_2$$}$$)?

Accepted Answer

$$1 	imes 40.08\ \mathrm{amu} + 2 	imes 35.453\ \mathrm{amu} = 110.99\ \mathrm{amu}$$

Question 5

A compound contains 61.31% C, 5.14% H, 10.21% N, and 23.33% O by mass. What is its empirical formula?

Accepted Answer

$$\mathrm{C_7H_7NO_2}$$

Question 6

Which of the following statements about the mole is correct?

Accepted Answer

One mole of any substance contains $$6.02214 	imes 10$$^{23}$$ particles.

Question 7

Which of the following is a decomposition reaction?

Accepted Answer

$$2\mathrm{$$KClO_3$$}(s) \rightarrow 2\mathrm{KCl}(s) + \mathrm{O_2$}(g)$$

Question 8

A 0.1000 g sample of a compound containing only C, H, and O burns to produce 0.227 g CO$$_2$$ and 0.0930 g H$$_2O. $$What is the empirical formula of the compound?

Accepted Answer

$$\mathrm{C_3H_6O}$$

Question 9

Which of the following is the correct percent composition by mass of oxygen in oxalic acid ($$\mathrm{H_2C_2O_4}$$)?

Accepted Answer

71.08%

Question 10

Which of the following best describes a combination reaction?

Accepted Answer

Two or more substances react to form one product.

Question 11

If the empirical formula of a compound is $$\mathrm{C_4H_8O}$$ and its molar mass is 216 g/mol, what is its molecular formula?

Accepted Answer

$$\mathrm{C$$_{12}$$H_{24}O_3$}$$

Question 12

Which of the following is the correct balanced equation for the reaction of solid calcium phosphate with aqueous sulfuric acid?

Accepted Answer

$$\mathrm{Ca_3$(PO_4$)_2(s) + 3H_2SO_4(aq) \rightarrow 3CaSO_4(s) + 2H_3PO_4(aq)}$$

Question 13

Which of the following is the correct definition of molar mass?

Accepted Answer

The mass of one mole of a substance, expressed in g/mol.

Question 14

Which of the following ions is a polyatomic anion commonly used in airbags?

Accepted Answer

Azide ion ($$\mathrm{N_3$^-})$$

Question 15

Which of the following is the correct mole relationship for 1 mole of $$\mathrm{NaCl}$$?

Accepted Answer

1 mole of $$\mathrm{NaCl}$$ contains $$6.022 	imes 10$$^{23}$$ formula units.

Question 16

A magnesium oxide sample is found to be 60.3% Mg by mass. What is its empirical formula?

Accepted Answer

$$\mathrm{MgO}$$

Question 17

Which of the following best describes a combustion reaction?

Accepted Answer

A rapid reaction with oxygen that produces a flame.

Question 18

Which of the following is the correct percent composition by mass of carbon in oxalic acid ($$\mathrm{H_2C_2O_4}$$)?

Accepted Answer

26.68%

Chemical Equations, Stoichiometry, and the Mole: Foundations of Quantitative Chemistry

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