Question

a chemist measures the energy change $\delta h$ during the following reaction:
\\2\\,\text{nh}_3(g) \
ightarrow \text{n}_2(g) + 3\\,\text{h}_2(g)\quad\quad \delta h = 160.\\,\text{kj}\\
use the information to answer the following questions.
| this reaction is... | $\circ$ endothermic.
$\circ$ exothermic. |
| suppose $97.8\\,\text{ g}$ of $\text{nh}_3$ react.
will any heat be released or absorbed? | $\circ$ yes, absorbed.
$\circ$ yes, released.
$\circ$ no. |
| if you said heat will be released or absorbed in the second part of this question, calculate how much heat will be released or absorbed.
round your answer to $3$ significant digits. | $\square\\,\text{kj}$ |

Explanation:

Step1: Identify reaction type

Endothermic (ΔH > 0)

Step2: Molar mass of NH₃

Molar mass = 14.01 + 3×1.008 = 17.034 g/mol

Step3: Moles of NH₃ reacted

Moles = 97.8 g / 17.034 g/mol ≈ 5.741 mol

Step4: Heat per 2 moles NH₃

ΔH for 2 mol NH₃ = 160 kJ

Step5: Calculate heat absorbed

Heat = (5.741 mol / 2 mol) × 160 kJ ≈ 459 kJ

Answer:

This reaction is...: endothermic
Suppose 97.8 g of NH₃ react. Will any heat be released or absorbed?: Yes, absorbed
If you said heat will be released or absorbed...: 459 kJ