Question

Thermochemistry problem?

Answer 1

C. `x = "12 °C"`.

Explanation:

Experiment I

`"Moles of each reactant" = 100.0 color(red)(cancel(color(black)("cm"^3))) × "1.0 mmol"/(1 color(red)(cancel(color(black)("cm"^3)))) = "100 mmol"`

`"Total volume of solution = 200.0 cm"^3`

`ΔT = "6.0 °C"`

Experiment II

`"Moles of each reactant" = 50.0 color(red)(cancel(color(black)("cm"^3))) × "2.0 mmol"/(1 color(red)(cancel(color(black)("cm"^3)))) = "100 mmol"`

`"Total volume of solution = 100.0 cm"^3`

`ΔT = ?`

In Experiment II, you used the same number of moles of reactants as in Experiment 1, so you generated the same amount of heat in each case.

In Experiment I, the temperature of `"200.0 cm"^3` of the solution increased by 6 °C.

In Experiment II, you generated the same amount of heat, but it had to heat only half as much solution (`"100.0 cm"^3`).

The temperature change should be twice that in Experiment I.

`"2 × 6 °C = 12 °C"`

∴ `x = "12 °C"`