AQA Jan 2012 Paper 4 Q4 (with explained solutions) |

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AQA Jan 2012 Paper 4 Q4

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do not write outside the box a this question involves calculations about two strong acids and one weak acid all measurements were carried out at oc a cm sample of mol dm hydrochloric acid was placed in a beaker and cm of distilled water were added calculate the ph of the new solution formed give your answer to decimal places marks extra space b hx is a weak monobasic acid b i write an expression for the acid dissociation constant ka for hx mark b ii the ph of a mol dm solution of hx is calculate a value for the acid dissociation constant ka of this acid give your answer to significant figures marks extra space wmp jan chem do not write outside the box c a cm sample of mol dm nitric acid was placed in a beaker and cm of mol dm aqueous sodium hydroxide were added calculate the ph of the solution formed give your answer to decimal places the ionic product of water kw mol dm at oc marks extra space turn over wmp jan chem

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b i b ii ka h x hx ignore ka h xh ka or h xh h or x ka sfs min allow if rounded to ignore units mark scheme general certificate of education a level chemistry unit kinetics equilibria and organic chemistry january marking guidance mark comments question a h ph dp allow m for correct ph calculation from their wrong h for this ph calculation only penalize missing here and not elsewhere allow ha instead of hx if h wrong can only score m allow ha instead of hx if hx used as this gives ka scores for ae m m m m m mark scheme general certificate of education a level chemistry unit kinetics equilibria and organic chemistry january c or mol oh mol h or excess mol oh oh or oh or poh h or ph allow sf m m m m m m mark for answer mark for answer allow conseq for m m if wrong method e g no subtraction or use of can only score max of m m m and m m m vol in dm mark for dividing by volume take use of without as ae so scores if no use or wrong use of vol lose m m can score m for showing their xs alkali if no use or wrong use of kw or poh no further marks if vol missed score max for if acid alkali reversed max for ph any excess acid max

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Topics to revise

AQA > Physical chemistry > Thermodynamics >

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