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8.P.1.4 - Balance Equations

Total questions: 37

Worksheet time: 1hrs 13mins

Name
Class
Date
1.

Which best describes how to balance the chemical equation Mg + O2 → MgO to support the law of conservation of mass?

a)
Add the coefficient 2 before the Mg on both sides of the equation.
b)
Add the coefficient 2 before the O2 on the left side of the equation.
c)
Add the coefficient 2 before the Mg on the left side of the equation.
d)
Add the coefficient 2 before the MgO on the right side of the equation.
2.

Zn + 2HCl → ZnCl2 + H2 In this equation, suppose 11 grams of zinc react with 12 grams of hydrogen chloride to form 16 grams of zinc chloride and an unknown amount of hydrogen gas. Based on the Law of Conservation of Mass, how many grams of hydrogen gas will form?

a)
7 grams
b)
1 gram
c)
19 grams
d)
39 grams
3.

The equation shows a reaction between sodium (Na) and water (H2O).

2Na (s) + H2O (l) → 2NaOH (aq) + H2 (g)

Which best explains why the equation is not balanced?

a)
There is not enough water in the reactants.
b)
There is too much sodium in the reactants.
c)
There is too much hydrogen gas in the products.
d)
There is not enough sodium hydroxide in the products.
4.

The reaction CaCO3 → CaO + CO2 takes place in a closed system. Which best describes this balanced equation?

a)
Reactants and products are equal in the chemical reaction.
b)
More products and less reactants are produced.
c)
More reactants and less products are produced.
d)
The equation is not balanced.
5.

Which products would balance the equation

CaCl2 + 2Li → ?

a)

none of these

b)
2LiCl + Ca
c)
LiCl + Ca
d)
Li2Cl + Ca
6.

A chemical reaction is represented by the equation

BeO + 2NaCl → Na2O + _______.

Which substance would make the equation true and balanced?

a)

BeCl2

b)
BeO
c)

Be2Cl

d)

3Be2Cl

7.

A chemical reaction is 2H2O → 2H2 + O2. Based on the law of conservation of mass, how much hydrogen gas is produced compared to the amount of oxygen produced?

a)
twice as much
b)
half as much
c)
the same amount
d)
four times as much
8.

What is the total number of oxygen atoms on the reactant side of the equation CH3COOH + NaHCO3 → CH3COONa + H2O + CO2?

a)
5
b)
2
c)
3
d)
7
9.

The chemical reaction 2H2O2 → 2H2O + O2 occurs. How many atoms of hydrogen are involved in the reaction?

a)
4
b)
1
c)
2
d)
8
10.

Sam followed the lab procedures shown in the image to complete an experiment. Which best describes Sam’s conclusion?

a)
No change in mass occurred after heating.
b)
A change in mass occurred after heating.
c)
A physical change occurred, producing new products.
d)
A chemical change occurred, producing new reactants.
11.

How many methane (CH4) molecules would be needed to produce 13 carbon dioxide (CO2) molecules?

{CH4 + 2O2 → CO2 + 2H2O}

a)
13
b)
4
c)
26
d)
52
12.

Which best explains how the chemical reaction 2H2 + O2 → 2H2O follows the law of conservation of mass?

a)
The same number of hydrogen and oxygen atoms are on both sides of the equation.
b)
The hydrogen and oxygen molecules combine to form water.
c)
Hydrogen and oxygen are held together by strong chemical bonds.
d)
There are hydrogen and oxygen atoms on both sides of the equation.
13.

If a chemical reaction starts with 10 times the amount of oxygen and hydrogen atoms shown, which best describes the amount of product? 2H2 + O2 → 2H2O

a)
There would be 10 times more water molecules produced.
b)
There would be 1 less water molecule produced.
c)
There would be 20 times more water molecules produced.
d)
There would be the same amount of water molecules produced.
14.

Which is the correct way to balance the chemical equation

Al + O2 → Al2O3?

a)

4Al + 3O2 → 2Al2O3

b)

2Al + O2 → Al2O3

c)

2Al + 3O2 → Al2O3

d)

4Al + 3O2 → Al2O3

15.

Max recorded the notes below as he completed an experiment in science class. Which best explains how the law of conservation of mass was demonstrated in the experiment?

a)
The mass of the resulting solution was equal to the mass of the solute and liquid.
b)
The solute completely dissolved in the liquid.
c)
The liquid was chemically changed by the addition of the solute.
d)
Some of the mass of the solute was lost during the experiment.
16.
Which best represents a balanced equation?
a)

2Mg(s) + O2(g) → 2MgO(s)

b)

Mg(s) + 2O2(g) → 2MgO(s)

c)

Mg(s) + O2(g) → 2MgO(s)

d)

3Mg(s) + 2O2(g) → MgO(s)

17.

How many copper atoms and how many chlorine atoms are in a molecule of CuCl2?

a)
one copper atom, two chlorine atoms
b)
one copper atom, one chlorine atom
c)
two copper atoms , one chlorine atom
d)
three copper atoms , two chlorine atoms
18.

One molecule of carbon dioxide (CO2) combines with one molecule of water (H2O) to make one molecule of carbonic acid. According to the Law of Conservation of Mass, how many atoms of carbon should be in the carbonic acid?

a)
1
b)
2
c)
3
d)
4
19.
Which equation is balanced according to the Law of Conservation of Mass?
a)

2NaCl + Mg → MgCl2 + 2Na

b)

NaCl + Mg → MgCl2 + Na

c)

2NaCl + Mg → MgCl2 + Na

d)

3NaCl + Mg → MgCl2 + 2Na

20.
Which equation satisfies the Law of Conservation of Mass?
a)

C3H8 + 5O2 → 3CO2 + 4H2O

b)

C3H8 + C3H8 → CC3H8 + H2O

c)

C3H8 + C3H8 → 3CC3H8 + 4H2O

d)
all of these
21.

The formula for glucose is C6H12O6. If glucose is broken down by a reaction, then how many atoms of carbon should be present in the products?

a)
6
b)
1
c)
12
d)
18
22.
Which best explains why the total mass of the product(s) would be less than the total weight of the reactant(s) after a chemical reaction?
a)
Gases were released to the atmosphere.
b)
A physical change occurred.
c)
Atoms involved in the reaction lost mass.
d)
Precipitates were created in the new solution.
23.
If a chemical reaction such as photosynthesis begins with 6 atoms of carbon (C), how many atoms of carbon (C) should be in the products?
a)
6 atoms of carbon (C)
b)
12 atoms of carbon (C)
c)
3 atoms of carbon (C)
d)
2 atoms of carbon (C)
24.
Which best represents a balanced equation?
a)
120 grams of carbon plus 80 grams of oxygen → 200 grams of carbon dioxide
b)
120 grams of carbon plus 20 grams of oxygen → 200 grams of carbon dioxide
c)
120 grams of carbon plus 50 grams of oxygen → 200 grams of carbon dioxide
d)
none of these
25.

The conversion of 7.0 grams of carbon monoxide and 7.5 grams of nitrogen monoxide using 3.0 grams of platinum catalyst is shown. Which best represents the total mass of carbon dioxide and nitrogen gases produced in this process?

a)

14.5 grams

b)

3.5 grams

c)

10.5 grams

d)

28.5 grams

26.
When chemicals react in a closed container, which must be true?
a)
The mass both before and after the reaction is the same.
b)
The mass both before and after the reaction is variable.
c)
The same number of compounds is present both before and after the reaction.
d)
No reaction will occur.
27.
Substance A has a mass of 7 grams. When substance A was mixed with substance B, a new substance was formed. Which statement best describes the Law of Conservation of Mass?
a)
The mass of the product is equal to the mass of the reactants.
b)
The mass of substance B is equal to the mass of the product.
c)
The mass of the product is less than the mass of the reactants.
d)
All of these
28.
The compound ammonia is composed of nitrogen and hydrogen atoms. If two atoms of nitrogen completely react with six atoms of hydrogen to form two molecules of ammonia, which best describes the number of hydrogen atoms present in the two molecules of ammonia?
a)
six hydrogen atoms
b)
two hydrogen atoms
c)
four hydrogen atoms
d)
eight hydrogen atoms
29.
Which must be true if the number of atoms stays the same regardless of how they are arranged?
a)
Their total mass stays the same.
b)
Their total mass must change.
c)
An open system must have been used.
d)
All of these
30.
A chemistry teacher combines 20 grams of lemon juice with 25 grams of baking soda in a flask covered with a balloon. The flask and balloon have a combined mass of 105 grams. What is the mass of the entire setup after a reaction has occurred?
a)
150 grams
b)
45 grams
c)
605 grams
d)
20 grams
31.
Which best supports the Law of Conservation of Mass?
a)
Atoms can be rearranged to keep the same mass.
b)
Atoms can be destroyed to make a new substance.
c)
Atoms can be rearranged to change their mass.
d)
All of these
32.
What best explains the result of substances of a chemical reaction?
a)
A new substance is produced.
b)
The same substance is produced.
c)
More energy is produced in the substance.
d)
Less energy is produced in the substance.
33.
What is the importance of a closed container in a chemical reaction?
a)
to observe the mass before and after the reaction occurs
b)
to keep any materials from interfering with the reaction
c)
to observe the loss of mass after the reaction occurs
d)
None of these
34.
A chemistry student combines 32 grams of one chemical and an unknown amount of another chemical in a closed system. A chemical reaction occurs and the mass of the products is 114 grams. How much of the unknown chemical was used in the reaction?
a)
82 grams
b)
32 grams
c)
114 grams
d)
97 grams
35.
Which best describes a chemical reaction applying the law of conservation of mass?
a)
a balanced equation in which the reactants and products are equal
b)
an equation which uses energy
c)
an equation which does not use energy
d)
an unbalanced equation in which the reactants and products are unequal
36.
Which are conserved during a chemical reaction?
a)
mass and atoms
b)
volume and mass
c)
atoms and molecules
d)
molecules and volume
37.
Element X reacts with element Y to form 250 g of XY. If no reactants are left over, which are most likely the amounts of X and Y in the reaction?
a)
75 g of X and 175 g of Y
b)
95 g of X and 115 g of Y
c)
100 g of X and 200 g of Y
d)
150 g of X and 300 g of Y

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