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.
actually..I know this is right. I don't need help with this one. Thank you.
Well, according to my calculations, I'd say you're almost there! Great job on determining the moles of H2O2 and using stoichiometry to find the total heat released. However, I noticed a minor mistake in your final answer.
You correctly found that the total heat released is 1.525542 x 10^6 kJ, but to properly round to three significant figures, we'll have to adjust it. Since the digit after the third significant figure (5) is 4 (less than 5), we leave the third significant figure (2) unchanged, making our final answer:
1.53 x 10^6 kJ
So, congratulations! You got it right and kept those sig figs in check. Keep up the good work!
Yes, you are correct. Your calculation is accurate. Let me explain the steps to find the answer to your question.
Step 1: Determine the moles of H2O2
To calculate the moles of H2O2, divide the mass of H2O2 by its molar mass. In this case, the mass of H2O2 is given as 529 kg, and the molar mass of H2O2 is 34 g/mol. Since the mass is given in kilograms, convert it to grams by multiplying by 1000.
529 kg × 1000 g/kg = 529,000 g
Moles of H2O2 = mass/molar mass
Moles of H2O2 = 529,000 g / 34 g/mol = 15,558.82 moles
Step 2: Calculate the total heat released
The balanced equation shows that 2 moles of H2O2 release 196.1 kJ of heat. Therefore, to find the heat released for 15,558.82 moles of H2O2, you need to multiply by a factor of:
Total heat released = (Hrxn / 2 moles) × (moles of H2O2)
Total heat released = (-196.1 kJ / 2 mol) × (15,558.82 mol)
Total heat released = -98.05 kJ/mol × 15,558.82 mol
Total heat released = -1,526,186.791 kJ
Step 3: Consider significant figures
The given value -196.1 kJ has four significant figures. Therefore, your final answer should also have four significant figures.
Rounding the answer to four significant figures, we get:
Total heat released = -1,526,186.791 kJ ≈ -1.526 × 10^6 kJ
So, the amount of heat released when 529 kg of H2O2 decomposes is approximately -1.526 × 10^6 kJ.