Question

The heat of neutralization of: 

(i) CHCl₂ –COOH by NaOH is 12830 cal; 

(ii) HCl by NaOH is 13680 cal 

(iii) NH₄ OH by HCl is 12270 cal. 

What is the heat of neutralization of dichloroacetic acid by NH₄ OH. Calculate also the heats of ionization of dichloroacetic acid and NH₄ OH. 

Answer 1

CHCl₂ – COOH by NaOH = 12850

HCl by NaOH is 13680

NH₄ OH by HCl is 12270

CH Cl₂ COOH + NaOH → CHCl₂ COONa + H₂O

NH₄OH + HCl → NH₄ Cl + H₂O

NaOH +HCl → NaCl + H₂  gives

CHCl₂ +NH₄ OH → CH Cl₂ COONa + NH₄ Cl 

∴ ∆ H_reac = -12830 – 12270 +413680 = -11420

∆H_diss of CH Cl₂ COOH = 13680 – 12830 = 850

∆H_diss NH₄ OH = 13680 – 12270 = 1410.