A 69.0mL sample of 1.0 M NaOH is mixed with 58.0 mL of 1.0 M H2SO4 in a large St
ID: 957518 • Letter: A
Question
A 69.0mL sample of 1.0 M NaOH is mixed with 58.0 mL of 1.0 M H2SO4 in a large Styrofoam cup; the cup is fitted with a lid through which passes a calibrated thermometer. The temperature of each solution before mixing is 18.5 degrees Celcius. After adding the NaOH solution to the coffee cup, the mixed solutions are stirred until reaction is complete. Assume that the density of the mixed solutions is 1.00 g/mL, that the specific heat of the mixed solutions is 4.18 J/(g celcius), and that no heat is lost to the surroundings. The deltaHrxn for the neutralization of NaOH with H2SO4 is -114 kJ/mol H2SO4. What is the maximum measured temperature in the Styrofoam cup? I am doing something wrong when I solve for T can you show it step by step?
Explanation / Answer
2NaOH(aq) + H2SO4(aq) ----> Na2SO4(aq) + 2H2O(l)
No of mol of NaOH = 69/1000*1 = 0.069 mol
No of mol of H2SO4 = 58/1000*1 = 0.058 mol
limiting reactant is NaOH
No of mol of salt formed = 0.069/2 = 0.0345 mol
q released = -114*0.0345 = - 3.933 kj
3.933*10^3 = m*S*dT
MASS of solution = (69+58)*1 = 127 grams
3.933*10^3 = 127*4.18*(x-18.5)
x = final temperature = 25.91 C
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