Question

100 cm³ of 2.0 mol dm‐³ hydrochloric acid is poured into 100 cm³ of 2.0 mol dm‐³ sodium hydroxide solution. The initial and final temperature are immediately recorded as shown below. [Specific heat capacity = 4.2 J/g°C, density of solution = 1.0 gcm-3]. What is the value of heat released in the reaction?


initital temperature of hydrochloric acid: 29.0°C


initial temperature of sodium hydroxide solution: 29.0°C


highest temperature of the mixture: 35.0°C

Answer 1

1) HCl + NaOH → NaCl + H2O 

Moles (HCl) = Conc x Vol/1000 = 2.0*100/1000 = 0.2 moles

Moles (NaOH) = Conc x Vol/1000 = 2 * 100/1000 = 0.2 moles

2) Q = m*c*ΔT

Total mass of "water" = 200 g

ΔT = 35 - 29 = 6 K

Q= 200*6*4.2=5.04 kJ

3) ΔH_{neutralisation} =Q/moles of water made

ΔH_{neutralisation}=5.04/0.2 = 25.2 kJ