For each of the following, indicate the major species in solution, and whether t
ID: 704910 • Letter: F
Question
For each of the following, indicate the major species in solution, and whether they are acidic (pH7) or neutral (pH=7: (1.) Solution Major species Acidic, Is this a Basic or buffer? Neutral(yes/no) A. 15.0g of Na2HPO4 is dissolved in water to give 500.0mL of solution B. A solution that is 0.460M HF C. 7.5% m/m solution of D. 5.0mL of 1.0M Na0H is and 0.256M NaF. RbNO3 added to 15.00mL of 1.0M HC2H302 A mixture which is 0.300M aniline, C6HsNH2 and 0.300M C6HsNH3Cl E. F. 3.00mL of 1.0M HCl is added to 10.0 mL of the solution of part 1EExplanation / Answer
A) Na2HPO4 (aq) <--->2Na+ (aq) +HPO42- (aq) [dissociation in aqueous medium]
HPO42- (aq) +2H2O(l) <--> H3PO4 (aq) +2OH- [base hydrolysis]
HPO42- is a base as it can accept 2H+ ions, HPO42- +2H+--->H3PO4
major species: Na+ (neutral) ,HPO42- (basic)
Not a buffer, as conjugate acid H3PO4 produced by base hydrolysis is very less
B)HF (aq) +H2O(l) <--->F-(aq) +H3O+(aq) [acid and its conjugate base NaF are in equilibrium with respect to each other]
major species:HF(acidic) ,F-(basic)
As both conjugate base and acid are present , it is a buffer.
C) RbNO3 --->Rb+ +NO3- (complete dissociation in aqueous medium)
major species:Rb+, NO3- (both neutral)
Not a buffer
D) weak acid :CH3COOH(acetic acid)
Strong base is added to neutralize weak acid, CH3COOH(aq) +NaOH (aq)--->CH3COONa (aq) +H2O(l)
mol of NaOH added=0.0050L*1.0mol/L=0.005mol
mol of acetic acid present=0.015L*1.0 mol/L=0.015 mol
mol of acetic acid neutralized=mol of NaOH=0.005mol
mol of acetic acid remaining=0.015mol-0.005mol=0.010 mol
Major species:CH3COOH(acid), CH3COO- (basic)
It has both conjugate base and acid thus, it is a buffer.
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