Item 8 AA Manganese reacts with hydrochloric acid to produce manganese(II) chlor
ID: 927656 • Letter: I
Question
Item 8 AA
Manganese reacts with hydrochloric acid to produce manganese(II) chloride and hydrogen gas.
Mn(s)+2HCl(aq) MnCl2(aq)+H2(g)
When 0.600 g Mn is combined with enough hydrochloric acid to make 100.0 mL of solution in a coffee-cup calorimeter, all of the Mn reacts, raising the temperature of the solution from 23.9 C to 29.5 C.
Find Hrxn for the reaction as written. (Assume that the specific heat capacity of the solution is 4.18 J/gC and the density is 1.00 g/mL.)Express your answer using three significant figures.
Hrxn =________kJ
Explanation / Answer
Given,
Mass of Mn = 0.6 g
We know that Molar mass of Mn = 54.94 g / mol
=> Moles of Mn = 0.6 / 54.94 = 0.0109 moles
Volume of solution = 100 mL
Density of solution = 1 g / mL
=> Mass of solution = 100 mL x 1 g / mL = 100 g
Change in temperature of solution = 29.5 - 23.9 = 5.6 degree C
Specific heat capacity of solution = 4.18 J / g degree C
Heat absorbed by solution = 100 x 4.18 x 5.6 = 2340.8 J
Heat absorbed by solution = Heat released by the reaction
=> Heat released by the reaction = 2340.8 J
=> Heat released by reaction 0.0109 moles of Mn = 2340.8 J
=> Heat released by reaction 1 mole of Mn = 2340.8 / 0.0109 = 214752.3 J / mol = 214.75 kJ / mol
Therefore,
delta H rxn. = - 214.75 kJ (-ve since the heat is being released)
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