Energetics / Thermochemistry

To speed up the chemical reaction only

To ensure the temperature is uniform throughout the liquid

To increase the pressure in the cup

To prevent the chemicals from reacting too fast

It increases

It decreases

It stays the same

It drops to 0 °C

ΔH = q / n

ΔH = q × n

ΔH = m × c × ΔT

ΔH = n / q

$-250 \text{ kJ}$

$+250 \text{ kJ}$

$-50 \text{ kJ}$

$+50 \text{ kJ}$

$0 \text{ K}$

$273 \text{ K}$

$298 \text{ K}$

$373 \text{ K}$

Proportional to

Dependent on

Independent of

Determined by

The bonds in $CO_2$ and $H_2O$ are stronger than the bonds in $CH_4$ and $O_2$.

The bonds in $CH_4$ are stronger than the bonds in $CO_2$.

No bonds are broken during combustion.

Energy is absorbed when $CO_2$ is formed.

$348\text{ kJ mol}^{-1}$

$-348\text{ kJ mol}^{-1}$

$839\text{ kJ mol}^{-1}$

$0\text{ kJ mol}^{-1}$

$I_2(g) \rightarrow 2I(g)$

$H(g) + H(g) \rightarrow H_2(g)$

$CH_4(g) \rightarrow C(g) + 4H(g)$

$O_2(g) \rightarrow 2O(g)$