Apparatus:
Measuring cylinders, thermometer and plastic cup
Materials:
0.5 mol dm-3 silver nitrate solution, 0.5 mol dm-3 sodium chloride solution
Procedure: | ||
1. 25cm3 of 0.5 mol dm-3 sodium chloride solution is measured and poured into a clean and dry plastic cup using a measuring cylinder. 2. The initial temperature of sodium chloride solution is measured and then recorded. 3. Using another measuring cylinder, 25 cm3 of 0.5 mol dm-3 silver nitrate solution is measured. The initial temperature of the silver nitrate solution is measured after 5 minutes and recorded. 4. The silver nitrate solution is poured quickly and carefully into the sodium chloride solution. 5. The mixture is stirred with a thermometer throughout the experiment and the highest temperature obtained is recorded. | ||
Result: | ||
Mass, m | c | q |
= (25 + 25) g = 50 g | 4.2 | Initial temperature of sodium chloride solution = T1oC Initial temperature of the silver nitrate = T2 oC Highest temperature reached = T4 oC => Average initial temperature = (T1+T2)/2 = T3 oC è Increase in temperature, q = (T4 - T3) oC |
Calculation: | ||
No of moles of sodium chloride used | No of moles of silver nitrate used | |
= MV/1000 = 0.0125 mole | = MV/1000= 0.0125 mole | |
Chemical equation: AgNO3 (aq) + NaCl (aq) à AgCl (s) + NaNO3 (aq) Ionic equation: Ag + (aq) + Cl- (aq) à AgCl (s) 1 mole 1 mole 1 mole Heat released = mcq = (25 + 25 ) x 4.2 x (T4 - T3) = x J 0.0125 mole of AgCl precipitated releases x J of heat energy. Therefore, 1 mole of AgCl precipitated will released Heat of precipitation, DH = x/0.0125 J = y J Thermochemical equation: AgNO3 (aq) + NaCl (aq) à AgCl (s) + NaNO3 (aq) DH = - y/1000 kJmol-1 | ||
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