Question 1

Which of the following statements best explains why chemical equations must be balanced?

Accepted Answer

To ensure that the number of atoms of each element is the same on both sides, reflecting the conservation of mass.

Question 2

Given the unbalanced equation: $$\mathrm{C_3H_8} + \mathrm{O_2$} \rightarrow \mathrm{CO_2$} + \mathrm{H_2O}$$, what is the correct coefficient for $$\mathrm{O_2$}$$ when the equation is balanced?

Accepted Answer

5

Question 3

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

Accepted Answer

They indicate the relative minimum number of molecules or moles needed for the reaction to occur.

Question 4

In the reaction $$\mathrm{2Al} + 3\mathrm{$$CuSO_4$$} \rightarrow \mathrm{Al_2$(SO_4$)_3} + 3\mathrm{Cu}$$, what is the stoichiometric coefficient for $$\mathrm{Al}$$?

Accepted Answer

2

Question 5

A sample problem asks: If 96.1 g of propane ($$\mathrm{C_3H_8}) $$reacts with oxygen, what is the mass of $$\mathrm{O_2$}$$ required? (Molar mass of $$\mathrm{C_3H_8} = 44 g/$$mol). What is the first step in solving this problem?

Accepted Answer

Set up the balanced chemical equation for the reaction.

Question 6

Which of the following is the correct balanced equation for the reaction of hydrochloric acid with sodium bicarbonate?

Accepted Answer

$$\mathrm{HCl} (aq) + \mathrm{$$NaHCO_3$$} (s) \rightarrow \mathrm{CO_2$} (g) + \mathrm{H_2O} (l) + \mathrm{NaCl} (aq)$$

Question 7

Which of the following is NOT a correct physical state symbol used in chemical equations?

Accepted Answer

(p) for plasma

Question 8

In the reaction $$4\mathrm{NO_2$} (g) + \mathrm{O_2$} (g) + 2\mathrm{H_2O} (l) \rightarrow 4\mathrm{$$HNO_3$$} (aq)$$, if 16 kg of $$\mathrm{NO_2$} is $$used, what is the maximum mass of $$\mathrm{$$HNO_3$$}$$ that can be formed? (Molar mass: $$\mathrm{NO_2$} = 46 g/$$mol, $$\mathrm{$$HNO_3$$} = 63 g/$$mol)

Accepted Answer

21.9 kg

Question 9

Which of the following best describes a reactant in a chemical equation?

Accepted Answer

A substance present on the left-hand side of the arrow that is consumed during the reaction.

Question 10

When balancing the equation $$\mathrm{Al} + \mathrm{Co(NO_3$)_2} \rightarrow \mathrm{Al(NO_3$)_3} + \mathrm{Co}$$, what is the correct coefficient for $$\mathrm{Al}$$?

Accepted Answer

2

Question 11

Which of the following is a correct step in balancing a chemical equation?

Accepted Answer

Start by balancing the most complicated molecule (the one with the most atoms).

Question 12

If 2.18 moles of $$\mathrm{C_3H_8}$$ are combusted, how many moles of $$\mathrm{CO_2$}$$ are produced? (Balanced equation: $$\mathrm{C_3H_8} + 5\mathrm{O_2$} \rightarrow 3\mathrm{CO_2$} + 4\mathrm{H_2O})$$

Accepted Answer

6.54 moles

Question 13

Which of the following is true about atoms in a chemical reaction?

Accepted Answer

Atoms are neither created nor destroyed; they are rearranged.

Question 14

In the reaction $$\mathrm{$$BaCl_2$$} (aq) + \mathrm{Na_2SO_4} (aq) \rightarrow \mathrm{$$BaSO_4$$} (s) + 2\mathrm{NaCl} (aq)$$, what is the physical state of $$\mathrm{$$BaSO_4$$}$$?

Accepted Answer

Solid (s)

Question 15

Which of the following is the correct mole ratio of $$\mathrm{C_3H_8} to$$ $$\mathrm{O_2$} in $$the balanced combustion equation $$\mathrm{C_3H_8} + 5\mathrm{O_2$} \rightarrow 3\mathrm{CO_2$} + 4\mathrm{H_2O}$$?

Accepted Answer

1:5

Question 16

A student balances the equation $$\mathrm{H_2$} + \mathrm{O_2$} \rightarrow \mathrm{H_2O} as$$ $$\mathrm{H_2$} + \mathrm{O_2$} \rightarrow \mathrm{H_2O_2}. $$What is the error in this approach?

Accepted Answer

The product identity was changed instead of adjusting coefficients.

Question 17

Which of the following best describes the process of balancing a chemical equation?

Accepted Answer

Adjusting the coefficients to ensure the same number of each type of atom on both sides.

Question 18

If 1 mole of $$\mathrm{Mg(OH)_2}$$ neutralizes 2 moles of $$\mathrm{HCl}$$, what is the balanced equation for this reaction?

Accepted Answer

$$\mathrm{Mg(OH)_2} + 2\mathrm{HCl} \rightarrow \mathrm{$$MgCl_2$$} + 2\mathrm{H_2O}$$

Question 19

Which of the following is a product in the reaction $$\mathrm{CH_4$} + 2\mathrm{O_2$} \rightarrow \mathrm{CO_2$} + 2\mathrm{H_2O}$$?

Accepted Answer

$$\mathrm{CO_2$}$$

Chemical Equations and Stoichiometry: Writing, Balancing, and Calculations

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