Question

23.6 g of calcium chloride (110.98) is dissolved in water in a calorimeter. T rose from 25.0°C to 38.7°C. Heat capacity of solution & calorimeter = 1258 J/°C. What is enthalpy change when 1 mol CaCl2 dissolves?

Answer 1

Enthalpy Change when 1 mole CaCl₂ dissolves

= - 81.13 kj/mole

Step-by-step explanation:

Given information

Mass of CaCl₂ = 23.6 g

Temperature changes from 25.0°C to 38.7°C

Heat capacity of solution & calorimeter (C) = 1258 J/°C

We know Q = C x ΔT

⇒ Heat released = 1258 x (38.7 - 25)

= 1.7234 x 10⁴ J

= 17.2 Kilo-joule

Thus 23.6 g is equivalent to 1.7234 x 10⁴ J or 17.2 Kilo-joule of heat energy

Molar mass of calcium chloride (110.98)

`Mole =(Mass)/(Molecular mass) = (23.6)/(110.98) =0.212 mole`

Enthalpy Change when 1 mole CaCl₂ dissolves

=
`(-17.2)/(0.212) kj/mol = -81.13 kj/mole`