Question

If 29.5 g of libr are dissolved 350.0 g of water at 20.0 °c in an insulated container, a temperature change is observed. the ∆h of solution of libr is -48.8 kj/mol. assuming that the specific heat of the solution is 4.184 j/(g °c), and that no heat is gained or lost by the container, what will be the final temperature of the solution

a) 15.3 °C
b) 20.0 °C
c) 27.8 °C
d) 30.7 °C

Answer 1

The final temperature is calculated by adding the temperature change to the initial temperature (20.0 °C).

Step-by-step explanation:

To find the final temperature of the solution after dissolving LiBr, we need to calculate the heat absorbed or released by the solution and use it to find the temperature change. The energy change (ΔH) when 29.5 g of LiBr dissolves can be calculated using the given enthalpy of solution (ΔH of solution = -48.8 kJ/mol). This value is negative; hence the solution releases heat.

To find the moles of LiBr, we divide the mass by its molar mass (molar mass of LiBr = 86.85 g/mol): moles of LiBr = 29.5 g / 86.85 g/mol.

Then, we find the heat (q) released using ΔH: q = moles of LiBr × ΔH of solution. We then use the formula q = mcΔT to calculate the temperature change (ΔT), where m is the mass of water, c is the specific heat (assumed to be 4.184 J/(g °C) as for water), and ΔT is the change in temperature.

To find the final temperature after dissolving LiBr in water, calculate the moles of LiBr and the heat released, then use q = mcΔT to find the temperature change and add it to the initial temperature.