Question 1

Which of the following is NOT a sign of a chemical reaction?

Accepted Answer

Melting of ice

Question 2

Which symbol in a chemical equation indicates that a substance is dissolved in water?

Accepted Answer

$$(aq)$$

Question 3

What is the balanced chemical equation for the combustion of charcoal (carbon) in oxygen to form carbon dioxide?

Accepted Answer

$$C(s) + O_2$(g) \rightarrow CO_2$(g)$$

Question 4

According to the law of conservation of mass, which statement is TRUE for a balanced chemical equation?

Accepted Answer

The total mass of reactants equals the total mass of products.

Question 5

Balance the following equation: $$2Al(s) + 3CuCl_2(aq) \rightarrow 2AlCl_3(aq) + 3Cu(s). $$How many chlorine atoms are present on each side of the equation?

Accepted Answer

6 on the reactant side, 6 on the product side

Question 6

Which of the following elements is DIATOMIC in its natural state?

Accepted Answer

Oxygen

Question 7

What is the correct balanced equation for the formation of water from hydrogen and oxygen?

Accepted Answer

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

Question 8

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

Accepted Answer

They show the number of molecules or moles of each substance involved.

Question 9

A student observes bubbling and a temperature increase when mixing two solutions. What is the best conclusion?

Accepted Answer

A chemical reaction has occurred.

Question 10

Balance the following equation: $$C_3H_8 + O_2$ \rightarrow CO_2$ + H_2O. $$What are the correct coefficients?

Accepted Answer

$$1, 5, 3, 4$$

Question 11

Which of the following is a correct representation of a chemical reaction using state symbols?

Accepted Answer

$$NaCl(s) \rightarrow Na^+(aq) + Cl^-(aq)$$

Question 12

If 2 moles of $$Na_2SO_4$$ react with 2 moles of $$Ca(NO_3$)_2$$, how many moles of $$CaSO_4$$ are produced according to the balanced equation $$Na_2SO_4 + Ca(NO_3$)_2 \rightarrow 2NaNO_3 + $$CaSO_4$$?

Accepted Answer

2 moles

Question 13

Which of the following equations is balanced?

Accepted Answer

$$2Mg + O_2$ \rightarrow 2MgO$$

Question 14

What is the coefficient for $$O_2$$ when balancing the equation $$C_4H_{10} + O_2$ \rightarrow CO_2$ + H_2O$$?

Accepted Answer

6.5

Question 15

Which statement about diatomic elements is correct?

Accepted Answer

They exist as molecules containing two atoms.

Question 16

A chemical equation is balanced when:

Accepted Answer

The number of atoms of each element is the same on both sides.

Question 17

Which of the following is a correct balanced equation for the reaction of sodium oxide with water to form sodium hydroxide?

Accepted Answer

$$Na_2O + H_2O \rightarrow 2NaOH$$

Question 18

Which of the following is a real-world example of a chemical reaction?

Accepted Answer

Rust forming on iron

Question 19

If a chemical equation is not balanced, which law is being violated?

Accepted Answer

Law of Conservation of Mass

Question 20

Balance the following equation: $$C_2H_6O_2 + O_2$ \rightarrow CO_2$ + H_2O. $$What is the coefficient for $$O_2$$?

Accepted Answer

3

Chemical Reactions and Balancing Chemical Equations

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