Question

1. choose the best answer.

a reaction in which an electric current is required is called ______.
○ thermal decomposition
○ catalytic reaction
○ dissociation
○ electrolysis

1. choose the best answer.

which equation shows that heat has been added?
○ $\ce{s + o_{2} \leftrightarrow so_{2}}$
○ $\ce{ag + 2s \
ightarrow ags_{2}}$
○ $\ce{2k + i_{2} \
ightarrow 2ki + energy}$
○ $\ce{h_{2}o \stackrel{\delta}{\
ightarrow} h_{2} + o_{2}}$

Explanation:

Question 14

• Thermal decomposition needs heat, not electric current.
• Catalytic reaction needs a catalyst, not electric current.
• Dissociation is separation of ions, not requiring electric current.
• Electrolysis is a reaction where electric current drives a non - spontaneous reaction. So the reaction requiring electric current is electrolysis.

• The first option is a reversible reaction, no heat indication.
• The second is a simple combination, no heat indication.
• The third releases energy (exothermic), not adding heat.
• The fourth has $\Delta$ (heat symbol) above the arrow, meaning heat is added for the decomposition of water.

Answer:

D. electrolysis

Question 15