Liquid hydrogen peroxide, an oxidizing agent in many rocket fuel mixtures, releases oxygen gas on decomposition.
2 H2O2(l) 2 H2O(l) + O2(g) Hrxn = -196.1 kJ
How much heat is released when 529 kg H2O2 decomposes?
( ......... ) KJ
*note ..watch sig figs .
my work:
• 2 H2O2(l) => 2 H2O(l) + O2(g) ΔHrxn = -196.1 kJ
Moles of H2O2 = mass/molar mass
= 529,000/34 = 15558.82 moles of H2O2 release 196.1 kJ of heat
Total heat released = 15558.82/2 x196.1 = 1525542.301 = 1.52554 × 10^6
= 1.53 x 10^6 kJ (3 significant figures)
am I correct?.....thank you.
Your calculations are mostly correct, but there are a couple of errors in your final answer. Let's go through the steps:
1. Calculate the moles of H2O2:
moles = mass / molar mass = 529,000 g / 34 g/mol = 15,558.82 mol
2. Calculate the heat released per mole of H2O2:
ΔHrxn = -196.1 kJ
Heat released per mole = -196.1 kJ / 2 mol = -98.05 kJ/mol
3. Calculate the total heat released:
Total heat released = moles of H2O2 × heat released per mole
Total heat released = 15,558.82 mol × -98.05 kJ/mol = -1,524,740.891 kJ
4. Round the answer to three significant figures:
-1,524,740.891 kJ rounded to three significant figures is -1.52 × 10^6 kJ
So, the correct answer is -1.52 × 10^6 kJ (rounded to three significant figures).
Yes, your calculations are correct. Let's break down the steps to see how you arrived at the answer.
First, you correctly identified the balanced chemical equation for the decomposition of hydrogen peroxide:
2 H2O2(l) -> 2 H2O(l) + O2(g) ΔHrxn = -196.1 kJ
Next, you calculated the moles of hydrogen peroxide using its mass and molar mass:
Moles of H2O2 = mass/molar mass = 529,000/34 = 15,558.82 moles
Since the balanced equation shows that 2 moles of H2O2 release -196.1 kJ of heat energy, you can calculate the total heat released by multiplying the moles of H2O2 by -196.1 kJ per mole:
Total heat released = (15,558.82/2) x -196.1 = 1,525,542.301 kJ
Lastly, to adhere to the rules of significant figures, you round the answer to three significant figures:
1,525,542.301 kJ ≈ 1.53 x 10^6 kJ
Therefore, your final answer, 1.53 x 10^6 kJ, has three significant figures, which is the correct number of significant figures to use in the final result.
Well done on your calculations! If you have any more questions, feel free to ask.