0.243 g of magnesium metal is added to a beaker filled with 100.0 mL of 1.00 M H

Question

0.243 g of magnesium metal is added to a beaker filled with 100.0 mL of 1.00 M HCl at 21.2 degree C. If the density of the HCl solution is 1.01 g/mL and if Delta H = -464 kJ for the ensuing reaction (shown below), what is the temperature of the water when the reaction is complete. C_H2O, solid = 2.11 J/g* degree C; C_H2O, liquid = 4.18 J/g* degree C; C_H2O, gas = 1.89 J/g*degree C Mg(s) + 2HCl (aq) rightarrow MgCl_2(aq) H_2(g) Delta H_rxn = -464 kJ 10.6 degree C 21.2 degree C 32.2 degree C 42.2 degree C 1120 degree C

Explanation / Answer

Mass of Mg = 0.243 g.

molar mass of Mg = 24 g/mol

Moles of Mg = mass / molar mass = 0.243 / 24 = 0.0101 mol

So, deltaH for 0.0101 mol = - 464 * 0.0101 = - 4.82 kJ = - 4820 J

Mass of 100 mL solution = 1.01 * 100 = 101 g.

Total mass of mixture after addition of Mg = 100.243 g.

Specific heat of Solution = 4.184 J/K.g.

We, know, q = ms (t2-t1)

4820 = 100.243 * 4.184 ( t2 - 21.2)

4820 = 419.42t2 - 8891.6

t2 = 32.69 degree C

So, the answer is (c)

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