PARTF: A chemical compound has a molecular weight of 89.05 g/mole. 1.400 grams o
ID: 1041634 • Letter: P
Question
PARTF: A chemical compound has a molecular weight of 89.05 g/mole. 1.400 grams of this compound underwent complete combustion under constant pressure conditions in a special calorimeter. This calorimeter had a heat capacity of 2980 J °C.1 (Note that the calorimeter was made of a metal shell, a water "substitute" - a special oil, and a thermocouple). The temperature went up by 11.95 degrees. Calculate the molar heat of combustion of the compound . How much heat was given off by the combustion reaction, based on the temperature rise of the calorimeter? 2. How many moles of compound were used up to provide this heat? 3. How much heat would one mole of compound provide? 4. Is the combustion of this compound exothermic or endothermic? 5. Would the molar enthalpy of combustion for this compound be a negative quantity or a positive quantity?Explanation / Answer
1.
heat change = heat capacity of calorimeter * change in temperature
q = 2980 * 11.95
q = 35611 J
2.
Moles of compound = mass / molar mass = 1.400 / 89.05 = 0.0157 mol
3.
Heat given by one mole of compound = - q / n = - 35611 / 0.0157 = - 2268216 J/mol = - 2268.2 kJ/mol
4.
SInce energy is given off ( or temprerature is rised ) , the reaction is exothermic reaction
5.
It is a negative quantity.
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