Question 7.17: How much heat, in kilojoules, is released when nitrogen and ...

How much heat, in kilojoules, is released when nitrogen and hydrogen react to form 50.0 g of ammonia?

N2(g)+3H2(g)2NH3(g) N_{2}(g) + 3H_{2}(g) → 2NH_{3}(g)          ΔH = -92.2 kJ

The blue check mark means that this solution has been answered and checked by an expert. This guarantees that the final answer is accurate.
Learn more on how we answer questions.

STEP 1   State the given and needed quantities (moles).

ANALYZE THE PROBLEM Given Need Connect
50.0 g of NH3NH_{3} heat released, in kilojoules ΔH = – 92.2 kJ, molar mass
Equation
N2(g)+3H2(g)2NH3(g) N_{2}(g) + 3H_{2}(g) → 2NH_{3}(g)

STEP 2  Write a plan using t he heat of reaction and any molar mass needed.

grams of NH3   MolarMass   moles of NH3   Heat ofreaction  kilojoules grams  of  NH_{3}     \boxed{\begin{array}{l}\text{Molar}\\\text{Mass}\end{array}} →      moles  of  NH_{3}     \boxed{\begin{array}{l}\text{Heat of}\\\text{reaction}\end{array}} →    kilojoules

STEP 3  Write the conversion factors including heat of reaction.

1 mole of NH3=17.03 g of NH317.03 g NH31 mole NH3 and 1 mole NH317.03 g NH32 moles of NH3=92.2 kj92.2 kj2 moles NH3 and 2 moles NH392.2 kj \begin{array}{r c}\boxed{\begin{matrix} 1  mole  of  NH_{3}= 17.03  g  of  NH_{3}\\\frac{17.03  g  NH_{3}}{1  mole  NH_{3}} \text{ and } \frac{1  mole  NH_{3}}{17.03  g  NH_{3}} \end{matrix}} & \boxed{\begin{matrix}2  moles  of  NH_{3} = -92.2  kj \\ \frac{-92.2  kj}{ 2  moles  NH_{3}}\text{ and }\frac{2  moles  NH_{3}}{-92.2  kj} \end{matrix}}\end{array}

STEP 4   Set up the problem to calculate the heat.

50.0  g NH3Three SFs  ×  1 mole NH317.03 g NH3Four SFsExact  ×  92.2 kJ2 moles NH3ExactThree Sfs  =135 kJThree Sfs \underset{Three  SFs }{50.0   \cancel{g  NH_{3}}}     \times    \overset{Exact}{\underset{Four  SFs }{\boxed{\frac{1  \cancel{mole  NH_{3}}}{17.03  \cancel{ g  NH_{3}}} }}}   \times    \overset{Three  Sfs }{\underset{Exact }{\boxed{\frac{-92.2  kJ}{2  \cancel{ moles  NH_{3}}} }}}    = \underset{Three  Sfs }{-135  kJ}

Therefore, 135 kJ are released.

Related Answered Questions

Question: 7.10

Verified Answer:

STEP 1   State the given and needed quantities. ...
Question: 7.8

Verified Answer:

ANALYZE THE PROBLEM Given Need Connect formula o...
Question: 7.7

Verified Answer:

STEP 1   State the given and needed quantities. ...