Question

When pure sulfuric acid is dissolved in water, heat is evolved. In a laboratory experiment to measure the molar heat of solution of sulfuric acid, the following procedure was followed. To a calorimeter containing 3.00 × 102 g of water at 20.00 °C, 10.65 g of H2SO4, also at 20.00 °C was added. The tempera­ture change, which was monitored by a digital thermometer with negligible heat capacity, ceased when it reached a temperature of 26.55 °C. If the specific heat of the mixture is 4.184 J g‑1 °C‑1, and the small heat capacity of the calorimeter is ignored, what is the heat evolved, per mole of sulfuric acid? Show an overview of your work.

Answer 1

Answer: The amount of heat evolved per mole of sulfuric acid is 78104.7 Joules.

Step-by-step explanation:

We are given:

Mass of water =
`3.00* 10^2g=300g`

Mass of sulfuric acid = 10.65 g

To calculate the amount of heat evolved, we use the equation:

`q=mc\Delta T`

where,

m = mass of water + sulfuric acid = [300 + 10.65] = 310.65 g

c = specific heat capacity of mixture = 4.184 J/g.°C

`\Delta T` = change in temperature =
`T_2-T_1=26.55^oC-20^oC=6.55^oC`

Putting values in above equation, we get:

`q=310.65g* 4.184J/g.^oC* 6.55^oC\\\\q=8513.42J`

To calculate the number of moles, we use the equation:

`\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}`

Given mass of sulfuric acid = 10.65 g

Molar mass of sulfuric acid = 98 g/mol

Putting values in above equation, we get:

`\text{Moles of sulfuric acid}=(10.65g)/(98g/mol)=0.109mol`

Calculating the heat released per mole of sulfuric acid, we get:

`q=\frac{\text{Heat eveolved}}{\text{Moles of sulfuric acid}}\\\\q=(8513.42J)/(0.109mol)=78104.7J`

Hence, the amount of heat evolved per mole of sulfuric acid is 78104.7 Joules.