Construct a data table for Page 4 of this lab. Read the instructions for what to
ID: 511026 • Letter: C
Question
Construct a data table for Page 4 of this lab. Read the instructions for what to include. The table will not be turned in with the ASA but it may be checked during lab Use Hess's Law to show how equations 1-3 can be summed to obtain equation (Re-write each equation in the form necessary to produce equation 4, and show Hess' law by crossing out terms that cancel.) Refer to your textbook on how to do this. MgO(s) + 2 HCl_(aq) rightarrow MgCl_2(aq) + H_2O_(I) Delta H_1 Mg(s) + 2 HCl_(aq) rightarrow MgCl_2(aq) + H_2_(g) Delta H_2 H_2(g) + 1/2 O_2(g) rightarrow H_2O(I) Delta H_3 Mg(s) + 1/2 O_2_(g) rightarrow MgO(s) Delta H_4 Write an equation for how Delta H_4 will be solved using the terms Delta H_1, Delta H_2, and Delta H_3(Example: Will Dleta H_4 = Delta H_1 - Delta H_2 + Delta H_3? Or Delta H_1 + Delta H_2 + Delta H_3? etc..) A student measures out 100.0 ml of 1.00 M HCl and places it in a styrofoam cup. The temperature of the HCl is 22.3 degree C. She then addes 1.002 g of MgO to the cup. The temperature rises to 29.7 degree C. Determine the enthalpy of the reaction. Assume that the density and the specific heat of the solution are the same as water. Include the correct sign. Determine the change of enthalpy for the reaction in units of kJ per mol of MgO. Include the correct sign!Explanation / Answer
2a) Hess's law
Add equations (2) and (3),
Mg(s) + 2HCl(aq) + 1/2O2(g) --> MgCl2(aq) + H2O(l)
invert (1) and add to this equation,
MgCl2(aq) + H2O(l) --> MgO(s) + 2HCl(aq)
------------------------------------------------------------------------
Mg(s) + 1/2O2(g) --> MgO(s)
So,
2b) dH for (4) = -dH1 + dH2 + dH3 = dH4
3) enthalpy
a) Enthalpy dH = -mCpdT
with,
m = 100 + 1.002 = 101.002 g
Cp = 4.18 J/oC.g
dT = 29.7 - 22.3 = 7.4 oC
we get,
dH = -101.002 x 4.18 x 7.4/1000
= 3.124 kJ
b) Enthalpy per mole of MgO
= 3.124 x 40.3044/1.002
= 125.67 kJ/mol