Question

17. Which of these acids is the strongest? A) H2SO3 B) H2SO3 C) H2TeO3 18. Which one of these net ionic equations represents the reaction of a strong acid with a weak base? A) H(aq) + OH(aq) + H2O(aq) B) H(aq) + CH3NH2(aq) → CH3NH3(aq) C) OH(aq) + HCN(aq) → H2O(aq) + CN-(aq) D) HCN(aq) + CH3NH2(aq) → CH3NH3+ (aq)+ CN (aq) 19. Predict the direction in which the equilibrium will lie for the reaction H2CO3 + HCO,- + HF. K(H2CO3) -4.2 x 10-7; K,(HF) - 7.1 x 10-4 A) to the right B) to the left C) in the middle 20. Consider a buffer solution prepared from HOCI and NaOCI. Which is the net ionic equation for the reaction that occurs when NaOH is added to this buffer? A) OH + HOCI H20+ OCH B) OH + OCHOCI + O2- C) Na+ + HOCI - NaCl + OH D) H + HOCI H2 + OCE E) NaOH + HOCI → H2O + NaCl

Answer 1

17) H2SO3, H Se0z and H Te03 The acidity of the oxyacid depends on the electronegativity of the central atom. As the electronegativity increases, the-O-H bond will be weaken and thus increases the acidity. Among S, Se and Te, Sis more electronegative atom and thus HSOis more acidic than H2SeO3 and H2TeO3 H2SO3 > H2SeO3 > H, Teo Option A is the right answer. 18. CH3NH2 is a weak base, HCN is a weak acid The reaction of strong acid and weak base is H+ (aq) + CH3NH2 (aq) ---------> CH3NH3+ (aq) Option B is the right answer.

19. Ka of HF is greater than Ka of H2CO3 So, HF is stronger acid than H2003 Hence HF donates proton easity than H2CO3 For the reaction, H2CO3 + F-<--------> H2CO3- + HF The equilibrium shift to the left side as HF donates proton (as it is stronger acid) Option B is the right answer. 20. When NaOH adds to the buffer solution, it reacts with HOCl to form OCl-. So the conc. of Ocl-increases and conc. of HOCI decreases. Net ionic equation is OH + HOCI ----------> H2O + clo- Option A is the right answer.