Lab 10-Calorimetry and the Enthalpies of Neutralization Pre-lab Questions 2. A 5
ID: 559575 • Letter: L
Question
Lab 10-Calorimetry and the Enthalpies of Neutralization Pre-lab Questions 2. A 50.00 mL sample of 0.5012 M KOH at 21.3 °C was added to a calorimeter containing 5000 mL of 0.4998 M HCl at 22.4 °C· (The densities of these diluted solutions can be determined by using the appropriate temperatures and densities located in Table 10.1. Note that the units for density in those tables are in kg/m Convert your densities to gmL before usel) The maximum temperature, 252°C, of the resulting reaction was determined graphically. The heat capacity of the calorimeter was 46.19 JC. For the following reaction, calculate the indicated values. Calculations 1 pt) (1 pt) (3 pts) Limiting Reagent moles 3 pts 3 pts) 13 3. Why is skin contact with a basic solution more dangerous than contact with an acidic solution at equimolar concentration? Total 30 272Explanation / Answer
mass acid = MV = D*V = 5*1 = 50 g
mass base = 50*1 = 50 g
mass solution = 50+50 = 100 g
assume initial T= average = (21.3+22.4)/2 = 21.85°C
dT = 25.2-21.85 = 3.35
Q = m*C*dT + Ccal*dT
Q = 100*4.18*3.35 + 46.19*3.35 = 1555.03 J
limiting reagent moles -->
mmol base = MV = 0.5012*50
mmol acid = MV = 0.4998*50 = 24.99
mol = 24.99*10^-3 acid
HRxn = Q/mol = - 1555.03 / ( 24.99*10^-3) = -62226.09J/mol = -62.22 kJ/mol
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