Zinc metal reacts with hydrochloric acid according to the following balanced equation.

zn(s)+2hcl(aq)→zncl2(aq)+h2(g)

when 0.121 g of zn(s) is combined with enough hcl to make 52.5 ml of solution in a coffee-cup calorimeter, all of the zinc reacts, raising the temperature of the solution from 21.8 ∘c to 23.9 ∘c. find the enthalpy change (in kj/mol) for this reaction as written. (use 1.0g/ml for the density of the solution and 4.18 j/g *celcius as the specific heat capacity.)

The enthalpy change is  -249.1 kJ/mole

Explanation:

Step 1: The balanced equation

Zn(s)+2HCl(aq)→ZnCl2(aq)+H2(g)

Step 2: Data given

mass of Zn = 0.121 grams

volume of the solution = 52.5 mL = 0.0525 L

Initial temperature = 21.8°C

Final temperature = 23.9 °C

Density of the solution = 1g/mL

Specific heat capacity = 4.18 J/ g°C

Step 3: Calculating mass of solution

mass = density * volume

mass = 1g/ mL * 52.5 mL = 52.5 grams

Step 4: Calculate heat transfer

Q = m*c*ΔT

with m = mass of the solution = 52.5 grams

with c= the specific heat capacity of the solution = 4.18 J/g °C

with ΔT = the change in temperature = final - initial temperature = 23.9 - 21.8 °C = 2.1 °C

Q = 52.5 grams * 4.18 J/g°C * 2.1 °C = 460.845 J

Step 5: Calculate number of moles of Zn

moles = mass of Zinc / Molar mass of Zinc

moles of Zinc = 0.121 grams / 65.38 g/mol = 0.00185 moles

Step 6: Calculate enthalpy change

ΔHrxn = heat / moles

ΔHrxn = 460.845 J / 0.00185 moles = 249105.4 J/mole = 249.1 kJ/mole

Since reaction is exothermic, ΔHrxn is negative.

ΔHrxn = -249.1 kJ/mole

OK so, "question" 1 and 2 are an example question of the relationship between mass, volume, and density and they work you through the problem and answer it for you so... you should probably probably just read it.