Question

You mix 125 mL of 0.170 M with 50.0 mL of 0.425 M in a coffee-cup calorimeter, and the temperature of both solutions rises from 20.20 °C before mixing to 22.17 °C after the reaction. What is the enthalpy of reaction per mole of ? Assume the densities of the solutions are all 1.00 g/mL, and the specific heat capacities of the solutions are 4.2 J/g · K. Enthalpy of reaction = kJ/mol

Answer 1

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You mix 125 mL of 0.170 M CsOH with 50.0 mL of 0.425 M HF in a coffee-cup calorimeter, and the temperature of both solutions rises from 20.20 °C before mixing to 22.17 °C after the reaction. What is the enthalpy of reaction per mole of ? Assume the densities of the solutions are all 1.00 g/mL, and the specific heat capacities of the solutions are 4.2 J/g · K. Enthalpy of reaction = kJ/mol

Answer:

75.059 kJ/mol

Explanation:

The formula for calculating density  is:

$density = \frac{mass}{volume}$

Making mass the subject of the formula; we have :

mass = density × volume

which can be rewritten as:

mass of the solution =  density × volume of the solution

= 1.00 g/mL × (125+ 50 ) mL

= 175 g

Specific heat capacity = 4.2 J/g.K

∴ the energy absorbed is = mcΔT

= 175 × 4.2 × (22.17 - 20.00) ° C

= 1594.95 J

= 1.595 J

number of moles of CsOH =  $\frac{125}{1000} *100$

= 0.2125 mole

Therefore; the enthalpy of the reaction = $\frac{Energy \ absorbed }{number \ of \ moles}$

= $\frac{1.595}{0.02125}$

= 75.059 kJ/mol