A coffee cup calorimeter contains 0.0375 mol HCl dissolved in 1.50 x 10^2 mL of water at 20.51 C. When 1.75 g of solid zinc metal is placed in the calorimeter, the temperature rises to 29.02 C. Assume that no heat is lost to the surroundings.

A coffee cup calorimeter contains 0.0375 mol HCl dissolved in 1.50 x 10^2 mL of water at 20.51 C. When 1.75g of solid zinc metal is placed in the calorimeter, the temperature rises to 29.02 °C.  Assume that no heat is lost to the surroundings.

Write the balanced equation for the reaction that takes place in the calorimeter.  1pt

Balanced reaction

Zn (s)  + 2 HCl (aq) --> ZnCl₂(aq) + H2 (g)

Find the limiting reactant. Show your work. 2 pts.

Number of moles of Zn             = given mass of Zn / molar mass of Zn

                                                  = 1.75 g Zn / 65.3.9 g/mol

                                                  = 0.02676 moles Zn

In equation 1 mole of Zn react with 2 mol of HCl

Hence  0.02676 moles Zn react with        = 2  x 0.02676

                                                             = 0.05352 mol of HCl 

But required moles of HCl (0.05352 mol) > given moles (0.0375)

Hence HCl is limiting reagent

Find the amount of heat lost or gained by the calorimeter. Show your work. 2pts.

Formula of heat change, ∆T       = T₂ - T₁ = 29.02 - 20.51  = 8.51 ° C

Specific heat capacity for water , C = 4.184 J/g-C

Mass of water m                            = 1.50 x 10²  ml = 150 g  (for water 1 ml = 1 g )

Use formula of enthalpy change ∆H = m * C *∆T

Plug the values

                                               ∆H = 150 g  x 4.184 J/g-C  x 8.51 C

∆H = 5341 Joules         

Divide by 1000 to convert in kJ 

                                                ∆H = 5.34 KJ

Temperature is increasing so that it is a exothermic reaction

And for all exothermic reaction ∆H is always negative 
energy lost by reaction and gained by solution.  hence calorimeter gain this energy

 So final answer will ∆H = - 5.34 KJ