Chemistry 2000 JAMB Past Questions - Question 28: 0.46g of ethanol when burned raised the temperature of 50 g of water by 14.3 K. Calculate the heat of combustion of ethanol. .

Correct Answer

C

Explanation

Heat=-MCQ =-50*4.2*14.3 =-300kJmol
To calculate the heat of combustion of ethanol, we can use the formula:

\(q = mc\Delta T\)

Where:
\(q\) = heat energy
\(m\) = mass of water
\(c\) = specific heat capacity of water
\(\Delta T\) = change in temperature

First, we can calculate the heat energy released by the burning of ethanol using the given data. The specific heat capacity of water, \(c\), is 4.18 J/g°C.

\(q = (50g)(4.18 J/g°C)(14.3 K)\)
\(q = 3011 J\)

This heat energy, 3011 J, is released by the burning of 0.46g of ethanol.

Now, we can calculate the heat of combustion of ethanol using the formula:

\(\text{Heat of combustion} = \frac{q}{\text{mass of fuel burned}}\)

\(\text{Heat of combustion} = \frac{3011 J}{0.46g}\)
\(\text{Heat of combustion} \approx 6543.48 J/g\)

So, the heat of combustion of ethanol is approximately 6543.48 J/g.