Friday, January 22, 2016

Calculate the amount of heat (in kJ) required to raise the temperature of 186 grams of water from 29◦C to 69◦C. (The specific heat of water is...

Specific heat is the amount of heat required to raise the temperature of one gram of a substance one degree celsius. The equation for calculating the amount of heat required for a given temperature change in a given mass of substance is:


q = mc `Delta` T  where:


q = heat 


m = mass = 186g


c = specific heat = 4.186 Joules/gram-ºC


 `Delta` T = change in temperaturge = 69ºC-29ºC = 4ºC


q =...

Specific heat is the amount of heat required to raise the temperature of one gram of a substance one degree celsius. The equation for calculating the amount of heat required for a given temperature change in a given mass of substance is:


q = mc `Delta` T  where:


q = heat 


m = mass = 186g


c = specific heat = 4.186 Joules/gram-ºC


 `Delta` T = change in temperaturge = 69ºC-29ºC = 4ºC


q = (186 g)(4.186 J/g-ºC)(40ºC) = 31,099 J = 31,000 J rounded to 2 significant digits.


To change this value to kilojoules, multiply by the conversion factor 1kJ/1000 J:


(31,000 J)(1 kJ/1000 J) = 31 kJ


Another method of calculating the answer is kJ is to change the specific heat of water to kJ/g-ºC:


(4.186 J/g-ºC)(1 kJ/1000 J) = .004186 kJ/g-ºC


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