Question 1

Which of the following is NOT a sign that a chemical reaction has occurred?

Accepted Answer

Melting of ice

Question 2

What does the symbol $$(aq)$$ represent in a chemical equation?

Accepted Answer

Aqueous, meaning dissolved in water

Question 3

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

Accepted Answer

Oxygen ($$O_2)$$

Question 4

When balancing the equation $$2Al(s) + 3CuCl_2(aq) \rightarrow 2AlCl_3(aq) + 3Cu(s)$$, what is the total number of chlorine atoms on each side?

Accepted Answer

6

Question 5

Which law states that the total mass of reactants must equal the total mass of products in a chemical reaction?

Accepted Answer

Law of Conservation of Mass

Question 6

Balance the following equation: $$C_2H_6O + O_2$ \rightarrow CO_2$ + H_2O. $$What is the correct set of coefficients?

Accepted Answer

$$1, 3, 2, 3$$

Question 7

A student observes bubbling and a temperature increase when mixing two clear solutions. Which evidence best supports that a chemical reaction occurred?

Accepted Answer

Formation of a gas and production of heat

Question 8

Which of the following equations is balanced?

Accepted Answer

$$2H_2 + O_2$ \rightarrow 2H_2O$$

Question 9

If 12 grams of carbon react with 32 grams of oxygen to form carbon dioxide, what is the mass of carbon dioxide produced according to the law of conservation of mass?

Accepted Answer

44 grams

Question 10

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

Accepted Answer

They indicate the relative number of molecules or moles of each substance

Question 11

What is the balanced equation for the combustion of butane ($$C_4H_{10}) in $$oxygen?

Accepted Answer

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

Question 12

Which statement is true about diatomic elements?

Accepted Answer

They exist as molecules containing two atoms in their natural state

Question 13

Balance the following equation: $$Na_2SO_4 + Ca(NO_3$)_2 \rightarrow $$NaNO_3$$ + $$CaSO_4$$. What are the correct coefficients?

Accepted Answer

$$1, 1, 2, 1$$

Question 14

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

Accepted Answer

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

Question 15

A student writes the equation $$H_2$$ + $$O_2$$ \rightarrow H_2O$$. What is wrong with this equation?

Accepted Answer

It is not balanced; there are more oxygen atoms on the reactant side

Question 16

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

Accepted Answer

To obey the law of conservation of mass

Question 17

Balance the following equation: $$MgBr_2$$ + $$Cl_2$$ \rightarrow $$MgCl_2$$ + $$Br_2. $$What are the correct coefficients?

Accepted Answer

$$1, 1, 1, 1$$

Question 18

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

Accepted Answer

Rust forming on iron

Question 19

What is the balanced equation for the reaction of sodium oxide with water to form sodium hydroxide?

Accepted Answer

$$Na_2O + H_2O \rightarrow 2NaOH$$

Question 20

Which of the following is the correct balanced equation for the reaction: $$C + O_2$ \rightarrow CO_2$?

Accepted Answer

$$1, 1, 1$$

Chemical Reactions and Balancing Chemical Equations

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