Question

worldwide, scientists are working on different options for clean energy to replace the burning of fossil fuels. one option that could potentially be successful is the use of hydrogen gas. this gas can be generated through a reaction between carbon and water.

$c(s)+2h_{2}o(g)longrightarrow co_{2}(g)+2h_{2}(g)delta h =?$

1. $co_{2}(g)longrightarrow c(s)+o_{2}(g)delta h = 393.5kj$

1. $2h_{2}o(g)longrightarrow 2h_{2}(g)+o_{2}(g)delta h = 483.6kj$

based on what you have learned in this lab, use the chemical equation and hesss law to determine the heat of formation and if this reaction is exothermic or endothermic.

Explanation:

Step1: Reverse reaction 1

$$\text{C(s)}+\text{O}_2(\text{g})\to\text{CO}_2(\text{g})\quad\Delta H=- 393.5\,\text{kJ}$$

Step2: Keep reaction 2 as it is

$$2\text{H}_2\text{O}(\text{g})\to2\text{H}_2(\text{g})+\text{O}_2(\text{g})\quad\Delta H = 483.6\,\text{kJ}$$

Step3: Add the two reactions

$$\text{C(s)}+2\text{H}_2\text{O}(\text{g})\to\text{CO}_2(\text{g})+2\text{H}_2(\text{g})$$
$$\Delta H=(-393.5 + 483.6)\,\text{kJ}$$

Answer:

$$\Delta H = 90.1\,\text{kJ}$$
Since $\Delta H>0$, the reaction is endothermic.