Hi there, I am suppose to calculate

**the enthalpy changes of Na2CO3 (anhydrous sodium carbonate) and NaHCO3 (sodium hydrogencarbonate)**, I have calculated them ( I think they are right, if they are not please help)

The two reactions carried out are

**A. 2HCl (aq) + Na2CO3(aq) → 2NaCl (aq) + CO2(g) + H2O(l)**

B. HCl (aq) + NaHCO3(aq) → NaCl (aq) + CO2(g) + H2O(l)I then am suppose to use hess's law, combining the results to obtain the enthalpy of reaction

**2NaHCO3(aq) ) → Na2CO3 (aq) + CO2(g) + H2O(l)***Now I will show you my working for just the enthalpy change of Na2CO3 *(because its really similar to NaHCO3)

*A 100 cm3 of 2 mol dm-3 hydrochloric acid was poured into a polystyrene cup. 8 grams of anhydrous sodium carbonate was added with.*

Initial temperature was 20.0 C and final temperature was 25.0 C.**(i) number of moles of HCl**1000 cm3 HCl solution contain 1 mol of HCl

Number of moles of HCl= MV/1000

M= molarity of the solution (mol dm-3)

V= volume of the solution (dm-3)

(2 x 100)/1000= 0.2 mol

**(ii) number of moles of Na2CO3**n= m/M

m= given mass (g)

M= molar mass(g mol-1)

M= (2.00 x 22.99) +(1.00 x 12.01) + (3.00 x 16.00)= 106.0 g mol-1

n= 8.00/106.0= 0.0755 moles (3 s.f.)

The ratio is 2 :1 so which means Na2CO3 is the limiting reactant.

**(iii) Delta temperature**

TFINAL-TINITIAL

25.0 ˚C - 20.0 ˚C= 5.0˚C (±1 ˚C)

**(iv) Heat released during reaction**

Q= mc ΔTm= 100 cm3= 100 ml

Density of water = 1 g mol

So in 100 ml, its 1 g mol x100 ml = 100 g

(100 g)(4.18 J/K.C)(5.0˚C)= 2090 Joules

Q= 2.09 kJ

ΔH=(-Q)/n

ΔH= -2.09/0.0755 = -27.7 kJ/ mol Na2CO3 (3 s.f.)

**ΔH= -27.7 kJ/ mol-1 (± 0.02) Na2CO3 (3 s.f.)**The enthalpy change I calculated for NaHCO3 (with the same method)

**I got ΔH= -22.5 kJ/ mol-1 (±0.03) NaHCO3**However I have to find a literature value and I've found one in the textbook

**Chemistry International Baccalaureate by John Green and Sadru Damji**The literature value in the book for enthalpy change is

**NaHCO3 is -140 kJ/ mol-1 and for Na2CO3 -370 kJ/mol-1****My values are very off from the literature value, so I don't know if I did something wrong but I thought I calculated it right... Please tell me if I did something wrong in my calculations and how to help fix them, because I first need to have the right calculations to combine the two to find the2NaHCO3(aq) ) → Na2CO3 (aq) + CO2(g) + H2O(l) **I know this is long so any help would be appreciated,

**thank you so much!**