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Hydrogen peroxide can decompose to water and oxygen by the following reaction: 2

ID: 950322 • Letter: H

Question

Hydrogen peroxide can decompose to water and oxygen by the following reaction: 2H_2O_2(l) rightarrow 2H_2O (I) + O_2(g) Delta H = -196kJ Calculate the value of q when 5.00 g of H_2O_2(l) decomposes at constant pressure. Large beds of rocks are used in some solar-heated homes to store heat. Assume that the specific heat of the rocks is 0.82 J/g degree C. Calculate the quantity of heat absorbed by 50.0 kg of rocks, if their temperature increases by 12.0 degree 0 What temperature change would these rocks undergo if they emitted 450 kJ of heat?

Explanation / Answer

from the reaction,

2 H2O2 ------> 2 H2O + O2

for 2 moles of H2O2 dH = 196 kJ

number of moles of H2O2 = 5 / 34 = 0.1471 moles

dH for 5 g H2O2 = (196 / 2) * 0.1471

dH for 5 g of H2O2 = 14.412 kJ