Question

[References] INTERACTIVE EXAMPLE Using a Coffee-Cup Calorimeter Suppose you place 0.0500 g of magnesium chips in a coffee cup calorimeter and then add 100.0 ml. of 1,00 M HC. The reaction that occurs is Mg(s) + 2 HCl(aq)-H2(g) + MgCl(aq) The temperature of the solution increases from 23.41 °C (296.56 K) to 25.66 °C (298.81 K) What is the enthalpy change for the reaction per mole of MR? Assume a specific heat capacity of the solution is 4.20 J/gK and the density of the HCl solution is 100 ml. kl/mol X Resubmit Show Approach Show Tutor Steps

Answer 1

Since temperature of the solution rises in both the cases, both reactions are exothermic in nature and ∆H is negative.

. 1) Heat change, Q = mass of solution x heat capacity of solution XAT = 100.5 x 4.20 I *(25.66 – 23:41)2. = 945. J Molar mass of mg = 24.3 g/mol So, 0.0500 g mg → aus I of heat R = 24.3 g mg - 945 x 24.3 J 0.0500 = u59270 J AH Down = -1 - 459270 J/mol F459.kJ/mol → 1000 J/kJ = 1-459.kJ/mol || 2) Vol. of solution Mays solution = (125 + 50 ML = 175 mL = v*d = 175. bat X 100 g =175.9 mt Now, heat change, Q = mass of solution x heat capacity of solution Xot = 175 g *4.2 *(23-87 –21.90). = 1.448 kJ Now, moles o CEOH = Molarity * volume = 0.170 M X 125 mL ; = 0.0212 . 1000 MLL Aloo, moles 9 HF = 0.425 M X 50.0 mL 1000 ml/l = 0' 02125 mol mol

Nou, о• о 21 25 hot Cs o4 1.448 kТ Э т ио Cgoи — Вт Т. 44 8 О•o2(25 р = 68 • kТ ДНhx = - 68.1 kJ mol