Part a The number of kilocalories in food is determined by calorimetry technique

Question

Part a

The number of kilocalories in food is determined by calorimetry techniques in which the food is burned and the amount of heat transfer is measured. How many kilocalories per gram are there in a 4.41-g walnut if the energy from burning it is transferred to 0.570 kg of water held in a 0.110-kg aluminum cup, causing a 52.3 C temperature increase?

Part b

If a serving of walnut consists of 18.0-g, how many kcal is consumed per serving( note: food packaging energy content is labeled as “Cal” which is equivalent to “kcal”.)

Explanation / Answer

Part A-

Specific heat capacity of water, s = 4200 J/kg.k, specific heat capacity of aluminium = 900 J/kg.K

So, amount of heat required to raise the temperature of 0.570 kg of water and 0.110 kg of Al by 52.3 deg C -

Q = m*s*delta T = 0.570*4200*52.3 + 0.110*900*52.3 = 130383.9 J = 130.384 kJ

Covert this in calories = 130383.9 / 4.184 = 31162.5 Cal.

Walnut energy in Kilo-Calorie/gm = 31162.5/(4.41x1000) = 7.066 kilocalories / gm.

(b) By consuming 18.0 g Walnut, amount of energy = 7.066 x 18 = 127.2 kilocalories. = 127.2 kcal.

Related Questions

Navigate

• Browse (All)
• Browse P
• Subjects