Balance It Right: Conservation of Atoms

Section A: Law of Conservation and Basic Balancing

Question 1mcq

A balanced chemical equation follows the law of:

A.Multiple proportions only

B.Conservation of speed

C.Conservation of mass

D.Reflection of light

Question 2mcq

Which is the balanced form of

H_2 + O_2 \rightarrow H_2O

?

A.

2H_2 + 2O_2 \rightarrow H_2O

B.

H_2 + 2O_2 \rightarrow H_2O

C.

H_2 + O_2 \rightarrow H_2O

D.

2H_2 + O_2 \rightarrow 2H_2O

Question 3mcq

Balance:

N_2 + H_2 \rightarrow NH_3

.

A.

N_2 + 3H_2 \rightarrow 2NH_3

B.

N_2 + H_2 \rightarrow NH_3

C.

2N_2 + H_2 \rightarrow 2NH_3

D.

N_2 + 2H_2 \rightarrow NH_3

Question 4mcq

Which coefficient is needed before

O_2

in

2Mg + O_2 \rightarrow 2MgO

?

A.2

B.4

C.3

D.1

Question 5mcq

Which balancing step is incorrect?

A.Placing 2 before

H_2O

B.Using coefficients before formulae

C.Counting atoms on both sides

D.Changing

H_2O

to

H_2O_2

to balance oxygen

Question 6mcq

If 12 g carbon reacts completely with 32 g oxygen to form carbon dioxide, the mass of

CO_2

formed is:

A.44 g

B.20 g

C.12 g

D.32 g

Section B: Polyatomic Ions, Combustion and Mistake Checks

Question 7mcq

Balance:

BaCl_2 + Na_2SO_4 \rightarrow BaSO_4 + NaCl

.

A.

2BaCl_2 + Na_2SO_4 \rightarrow BaSO_4 + NaCl

B.

BaCl_2 + Na_2SO_4 \rightarrow BaSO_4 + 2NaCl

C.

BaCl_2 + Na_2SO_4 \rightarrow 2BaSO_4 + NaCl

D.

BaCl_2 + 2Na_2SO_4 \rightarrow BaSO_4 + NaCl

Question 8mcq

Which is the balanced combustion equation for methane?

A.

CH_4 + 2O_2 \rightarrow CO_2 + 2H_2O

B.

CH_4 + 4O_2 \rightarrow CO_2 + H_2O

C.

CH_4 + O_2 \rightarrow CO_2 + H_2O

D.

CH_4 + O_2 \rightarrow C + H_2O

Question 9mcq

When balancing equations with unchanged sulphate ions, why can

SO_4

sometimes be counted as one unit?

A.Because oxygen cannot be counted

B.Because sulphate disappears

C.Because the sulphate group remains unchanged on both sides

D.Because coefficients cannot be used

Question 10mcq

A student writes

Fe + O_2 \rightarrow FeO_2

to balance oxygen. What is the mistake?

A.The formula of iron oxide was changed incorrectly

B.Iron cannot react with oxygen

C.Oxygen should never be written as

O_2

D.The arrow is missing

Question 11mcq

Balance:

C_3H_8 + O_2 \rightarrow CO_2 + H_2O

.

A.

C_3H_8 + 3O_2 \rightarrow 3CO_2 + 4H_2O

B.

3C_3H_8 + O_2 \rightarrow 3CO_2 + 4H_2O

C.

C_3H_8 + 5O_2 \rightarrow 3CO_2 + 4H_2O

D.

C_3H_8 + 5O_2 \rightarrow CO_2 + H_2O

Question 12mcq

Which equation is balanced?

A.

2KClO_3 \rightarrow 2KCl + 3O_2

B.

KClO_3 \rightarrow KCl + O_2

C.

2KClO_3 \rightarrow KCl + 3O_2

D.

KClO_3 \rightarrow 2KCl + O_2