Question 1

Which of the following best describes the activation energy ($E_a$) in a chemical reaction?

Accepted Answer

It is the minimum energy required for reactant molecules to collide and break bonds, allowing a reaction to occur.

Question 2

Consider the reaction: $2 	ext{H}_2(g) + 	ext{O}_2(g) \rightarrow 2 	ext{H}_2	ext{O}(g)$. Which law does this reaction illustrate when the number of atoms of each element is the same on both sides of the equation?

Accepted Answer

Law of Conservation of Mass

Question 3

Which of the following reactions is an example of an exothermic reaction?

Accepted Answer

$	ext{N}_2(g) + 3	ext{H}_2(g) \rightarrow 2	ext{NH}_3(g) + 92 	ext{ kJ}$

Question 4

A student balances the equation $2	ext{H}_2 + 	ext{O}_2 \rightarrow 2	ext{H}_2	ext{O}$ by changing the subscript in water to $2	ext{H}_2	ext{O}_2$. Why is this incorrect?

Accepted Answer

It changes the chemical identity of the product, violating the Law of Constant Composition.

Question 5

Which of the following is a correct balanced equation for the combustion of methane ($	ext{CH}_4$)?

Accepted Answer

$	ext{CH}_4(g) + 2	ext{O}_2(g) \rightarrow 	ext{CO}_2(g) + 2	ext{H}_2	ext{O}(g)$

Question 6

Which reaction type is illustrated by the following equation? $2	ext{KClO}_3(s) \rightarrow 2	ext{KCl}(s) + 3	ext{O}_2(g)$

Accepted Answer

Decomposition

Question 7

In the reaction $2	ext{AgNO}_3(aq) + 	ext{Na}_2	ext{SO}_4(aq) \rightarrow 2	ext{NaNO}_3(aq) + 	ext{Ag}_2	ext{SO}_4(s)$, what type of reaction is this?

Accepted Answer

Double replacement

Question 8

Which of the following statements about oxidation-reduction (redox) reactions is TRUE?

Accepted Answer

Oxidation is the loss of electrons, and reduction is the gain of electrons.

Question 9

Given the reaction $2	ext{Zn}(s) + 2	ext{HCl}(aq) \rightarrow 2	ext{ZnCl}_2(aq) + 	ext{H}_2(g)$, which element is oxidized?

Accepted Answer

Zn

Question 10

Which of the following is the correct set of coefficients to balance the equation: $	ext{Fe}_2	ext{O}_3(s) + 	ext{H}_2(g) \rightarrow 	ext{Fe}(s) + 	ext{H}_2	ext{O}(l)$?

Accepted Answer

1, 3, 2, 3

Question 11

Which of the following best describes a combination reaction?

Accepted Answer

A reaction in which two or more elements or compounds combine to form one product.

Question 12

In the reaction $2	ext{K}(s) + 2	ext{H}_2	ext{O}(l) \rightarrow 2	ext{KOH}(aq) + 	ext{H}_2(g)$, which element is reduced?

Accepted Answer

H

Question 13

Which of the following is NOT a guideline for balancing chemical equations?

Accepted Answer

Balance by changing the chemical identity of the reactants.

Question 14

Which of the following reactions is a single replacement reaction?

Accepted Answer

$	ext{Zn}(s) + 2	ext{HCl}(aq) \rightarrow 	ext{ZnCl}_2(aq) + 	ext{H}_2(g)$

Question 15

A reaction has an activation energy of $60$ kJ and a heat of reaction of $-250$ kJ. Which statement is correct?

Accepted Answer

The reaction is exothermic.

Question 16

Which of the following best describes the Law of Constant Composition?

Accepted Answer

A chemical compound always contains the same elements in the same proportion by mass.

Question 17

In the reaction $2	ext{Al}(s) + 3	ext{Cl}_2(g) \rightarrow 2	ext{AlCl}_3(s)$, how many chlorine atoms are present on the reactant side?

Accepted Answer

6

Question 18

Which of the following is the correct balanced equation for the reaction: $	ext{Mg}_3(	ext{PO}_4)_2 + 	ext{MgCl}_2 \rightarrow 	ext{Mg}_3	ext{Cl}_2 + 	ext{Mg}_2(	ext{PO}_4)_2$?

Accepted Answer

$2	ext{Mg}_3(	ext{PO}_4)_2 + 3	ext{MgCl}_2 \rightarrow 3	ext{Mg}_3	ext{Cl}_2 + 2	ext{Mg}_2(	ext{PO}_4)_2$

Question 19

Which of the following is a decomposition reaction?

Accepted Answer

$2	ext{KClO}_3(s) \rightarrow 2	ext{KCl}(s) + 3	ext{O}_2(g)$

Chemical Reactions: Types, Balancing, and Energy Changes – GOB Chemistry Study Notes

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