Question

using a food calorimeter a 0.11 g sample of brazil nut was burned. the water in the calorimeter (95g) had its temperature go from 19.5 C to 26.86 C. What is the caloric value for Brazil nuts in kcal/g?

Answer 1

Answer : The calorific value for Brazil nuts is 6.4 kcal/g

Explanation :

First we have to calculate the amount of heat released.

Formula used :

`Q=m* c* \Delta T`

or,

`Q=m* c* (T_2-T_1)`

where,

Q = heat released = ?

m = mass of water = 95 g

c = specific heat of water =
`1cal/g^oC`

`T_1` = initial temperature =
`19.5^oC`

`T_2` = final temperature =
`26.86^oC`

Now put all the given value in the above formula, we get:

`Q=95g* 1cal/g^oC* (26.86-19.5)^oC`

`Q=699.2cal=0.6992kcal`

conversion used : (1 kcal = 1000 cal)

Now we have to calculate the calorific value for Brazil nuts in kcal/g.

`\text{Calorific value}=\frac{\text{Heat released}}{\text{Mass of sample}}`

`\text{Calorific value}=(0.6992kcal)/(0.11g)=6.4kcal/g`

Therefore, the calorific value for Brazil nuts is 6.4 kcal/g

Answer 2

To determine the calorific value of the Brazil nuts, we first calculate the heat that is produced during the process from the given values above. Then, we divide the heat by the mass of the sample. We do as follows:

Heat = 95 g (4.18 J/g C) (26.86-19.5) = 2922.656 J or 2.92 kJ

Calorific value = 2.92 kJ/0.11g ( 1 kcal / 4184 kJ ) = 6.35x10^-3 kcal/g