Question 1

Which of the following is NOT considered evidence of a chemical reaction?

Accepted Answer

Bubbles form when water boils.

Question 2

What is the correct balanced chemical equation for the combustion of methane?

Accepted Answer

$$CH_4(g) + 2O_2(g$$) \rightarrow $$CO_2(g) + 2H_2O(g$$)$$

Question 3

Which of the following best describes a precipitation reaction?

Accepted Answer

A reaction in which a solid forms from two aqueous solutions.

Question 4

When sodium chloride ($$NaCl) $$dissolves in water, what is present in the solution?

Accepted Answer

Only $$Na^+$$ and $$Cl^-$$ ions

Question 5

Which of the following statements about strong electrolytes is correct?

Accepted Answer

They completely dissociate into ions in solution.

Question 6

Which of the following is a redox (oxidation-reduction) reaction?

Accepted Answer

$$2Na(s) + Cl_2$(g) \rightarrow 2NaCl(s)$$

Question 7

What is the main difference between a chemical change and a physical change?

Accepted Answer

A chemical change results in the formation of new substances, while a physical change does not.

Question 8

Which of the following is the correct sequence of steps for balancing a chemical equation?

Accepted Answer

Write correct formulas, balance elements that appear in only one compound on each side, balance free elements last, check your work.

Question 9

Which of the following compounds is insoluble in water?

Accepted Answer

$$AgCl$$

Question 10

A student mixes solutions of sodium carbonate ($$Na_2CO_3) $$and copper(II) chloride ($$CuCl_2). $$What is the balanced equation for the reaction, including states?

Accepted Answer

$$Na_2CO_3(aq) + $$CuCl_2$$(aq) \rightarrow $$CuCO_3$$(s) + 2NaCl(aq)$$

Question 11

Which of the following is a synthesis (combination) reaction?

Accepted Answer

$$2H_2(g) + O_2$(g) \rightarrow 2H_2O(g)$$

Question 12

Which of the following best describes a double-displacement reaction?

Accepted Answer

Two elements or groups in two compounds exchange places to form two new compounds.

Question 13

Which of the following is a correct statement about combustion reactions?

Accepted Answer

They are a type of redox reaction and are exothermic.

Question 14

What is the oxidation state of sodium in $$NaCl$$ after the redox reaction $$2Na(s) + Cl_2$(g) \rightarrow 2NaCl(s)$$?

Accepted Answer

+1

Question 15

Which of the following is a correct example of a single-displacement reaction?

Accepted Answer

$$Zn(s) + $$CuCl_2$$(aq) \rightarrow $$ZnCl_2$$(aq) + Cu(s)$$

Question 16

Which of the following observations would NOT be considered evidence of a chemical reaction?

Accepted Answer

A liquid evaporates, leaving a solid residue.

Question 17

What is the correct classification for the following reaction: $$2KClO_3(s) \rightarrow 2KCl(s) + 3O_2(g)$$?

Accepted Answer

Decomposition reaction

Question 18

Which of the following best explains why laundry detergent is more effective than soap in hard water?

Accepted Answer

Detergent reacts with calcium and magnesium ions to form solids that are removed from the water.

Question 19

Which of the following is the correct net ionic equation for the precipitation reaction between $$AgNO_3(aq$$)$$ and $$NaCl(aq)$$?

Accepted Answer

$$Ag^+(aq) + Cl^-(aq) \rightarrow AgCl(s)$$

Chapter 7: Chemical Reactions – Structured Study Notes

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