Chemistry Question, need help asap!

Question

During lab, a student mixed 25 mL of 1.0 M H3PO4 with 75 mL of 1.0 M NaOH. Using the equation below, determine how many moles of reaction the student performed.

 ____ moles of reaction

The intial temperature of both the acid and the base were 22.6 oC, but they rose to 28.2 oC during the reaction. If the calorimeter constant was 78.5 J/oC, what was qrxn in J?

_____ J

Using your answers above, what was the reaction enthalpy, ΔHrxn, in kJ per mol reaction?

 _____ kJ/mol of reaction

Answer 1

You didn't provide "the equation below" so I'll use my own.

moles H3PO4 = 25 m x 1 L/1000 ml x 1.0 mol/L = 0.025 moles H3PO4

moles NaOH = 75 ml x 1 L/1000 ml x 1.0 mol/L = 0.075 moles NaOH

Reaction: H3PO4 + 3NaOH ==> Na3PO4 + 3H2O

moles of reaction = 0.025 moles

q = Ccal x ∆T

q = heat = ?

Ccal = calorimeter constant = 78.5 J/º

∆T = change in temperature = 28.2 - 22.6 = 5.6º

q = 78.5 J/º x 5.6º = 439.6 J

∆Hrxn = 439.6 J / 0.025 moles = 17,584 J/mol = 17.6 kJ/mol