Mg reacts with H^+(aq) according to Mg(s) + 2H^+(aq) rightarrow Mg^2+(aq) + H_2(
ID: 498770 • Letter: M
Question
Mg reacts with H^+(aq) according to Mg(s) + 2H^+(aq) rightarrow Mg^2+(aq) + H_2(g) Suppose that 0.524 g of Mg is reacted with 60.0 mL of 1 0 M H^+(aq) according to the procedure used in this experiment. Assume that the density of the H^+(aq) solution is 1 00 g mL, and that its specific heat capacity equals that of water. The initial and final temperatures are 22.0 degree C and 65.8 degree C. (a) Is the reaction endothermic or exothermic? Explain. (b) Calculate the delta H of the reaction. Use the correct number of significant figures, and give units. (c) Calculate the delta H of the reaction per mole of magnesium.Explanation / Answer
a) it is exothermic reaction . because temperature increases from 22 oC to 65.8 oC.
b) moles of Mg = 0.524 / 24 = 0.0218
moles of HCl = 60 x 1 / 1000 = 0.06
Mg + 2 HCl -------------------> MgCl2 + H2
1 2
0.0218 0.06
Mg is limiting reagent
Q = m Cp dT
Q = 60 x 4.18 x (65.8-22)
Q = 10995 J
Q = 11.0 kJ
delta H = - Q / n
= -11.0 / 0.0218
= -504 kJ/ mol
c) here limiting reagent is Mg so both b and c answers same
delta H = = -504 kJ/ mol