Question

When 0.250 moles of KCl are added to 200.0 g of water in a constant pressure calorimeter a temperature change is observed. Given that the specific heat of the resulting solution is 4.184 J g-1 °C-1, the molar heat of solution of KCl is +17.24 kJ/mol, and that we can ignore the small amount of energy absorbed by the calorimeter, the observed temperature change should be Entry field with incorrect answer now contains modified data °C.

Answer 1

Step-by-step explanation:

Upon dissolution of KCl heat is generated and temperature of the solution raises.

Therefore, heat generated by dissolving 0.25 moles of KCl will be as follows.

`17.24 kJ/mol * 0.25 mol`

= 4.31 kJ

or, = 4310 J (as 1 kJ = 1000 J)

Mass of solution will be the sum of mass of water and mass of KCl.

Mass of Solution = mass of water + (no. of moles of KCl × molar mass)

= 200 g +
`(0.25 mol * 54.5 g/mol)`

= 200 g + 13.625 g

= 213.625 g

Relation between heat, mass and change in temperature is as follows.

Q =
`mC \Delta T`

where, C = specific heat of water =
`4.184 J/g^(o)C`

Therefore, putting the given values into the above formula as follows.

Q =
`mC \Delta T`

4310 J =
`213.625 g * 4.184 J/g^(o)C * \Delta T`

`\Delta T = 4.82^(o)C`

Thus, we can conclude that rise in temperature will be
`4.82^(o)C`.