AQA_AS Level Chemistry Paper 1_Mark Scheme 2022 | Practice Paper 1

Document Content and Description Below

AQA_AS Level Chemistry Paper 1_Mark Scheme 2022 | Practice Paper 1 1 (a) (i) [H+][OH−] OR [H3O+][OH−] 1 Ignore (aq) Must have [ ] not ( ) (ii) 3.46 × 10−14 (= 1.86 × 10−7) 2 If no squ... are root, CE= 0 pH = 6.73 Must be 2dp (iii) [H+] = 10−11.36 (= 4.365 × 10−12 OR 4.37 × 10−12) 1 Mark for working Kw = [4.365 × 10−12 OR 4.37 × 10−12 × 0.047] = 2.05 × 10−13 1 Allow 2.05 × 10−13 − 2.1 × 10−13 Mark for answer Ignore units (b) (i) HCOOH HCOO− + H+ 1 Must have but ignore brackets. OR HCOOH + H2O HCOO− + H3O+ Allow HCO2− or CHOO− ie minus must be on oxygen, so penalise COOH− (ii) 1 Must have all brackets but allow ( ) Must be HCOOH etc. Allow ecf in formulae from (b)(i) (iii) M1 1 Allow HA or HX etc. Allow [H+] = (Ka × [HA]) for M1 M2 [H+] = 3.16 × 10−3 1 Mark for answer M3 pH = 2.50 allow more than 2 dp but not fewer 1 Allow correct pH from their wrong [H+] here only If square root shown but not taken, pH = 5.00 can score max 2 for M1 and M3 - -- [Show More]

Last updated: 1 year ago

Preview 1 out of 7 pages