OCR A-level Chemistry - Paper 3
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1. Why does HF have a higher -Boiling point increases as electronegativity increases
boiling point than CH4? -HF has hydrogen bonding, CH4 has London forces
2. How do you prepare a stan- -Weigh out correct mass of solid
dard solution? -Dissolve in distilled water
-Transfer to a 250cm^3 volumetric flask
-Wash beaker with distilled water
-Add washings to the volumetric flask
-Make up to 250cm^3 with distilled water
-Invert to ensure mixing
3. Why can we sometimes as- Because it is in excess
sume a reaction in zero order
with respect to X?
4. How to test order of X from -Calculate half-life
concentration time graph? -If the next half-life is within 10s of the first, it is first order
5. Why is the reaction of Ethane Because further substitution can occur
with UV light a bad way to get
a high yield of Chloroethane?
6. Why are benzene bonds all They're all π bonds with one delocalised electron
the same length?
7. Why is the rate of hydroly- C-Br is weaker than C-Cl
sis of 1-bromobutane faster
than 1-chlorobutane?
8. Reactions on Fe2+ Mn2+ Fe(OH)2 pale green precipitate
NH4+ with aqueous NaOH Mn(OH)2 pale brown precipitate
NH3 + H2O red litmus paper turns blue from NH3 gas
1/3
Study online at https://quizlet.com/_bq49ju
1. Why does HF have a higher -Boiling point increases as electronegativity increases
boiling point than CH4? -HF has hydrogen bonding, CH4 has London forces
2. How do you prepare a stan- -Weigh out correct mass of solid
dard solution? -Dissolve in distilled water
-Transfer to a 250cm^3 volumetric flask
-Wash beaker with distilled water
-Add washings to the volumetric flask
-Make up to 250cm^3 with distilled water
-Invert to ensure mixing
3. Why can we sometimes as- Because it is in excess
sume a reaction in zero order
with respect to X?
4. How to test order of X from -Calculate half-life
concentration time graph? -If the next half-life is within 10s of the first, it is first order
5. Why is the reaction of Ethane Because further substitution can occur
with UV light a bad way to get
a high yield of Chloroethane?
6. Why are benzene bonds all They're all π bonds with one delocalised electron
the same length?
7. Why is the rate of hydroly- C-Br is weaker than C-Cl
sis of 1-bromobutane faster
than 1-chlorobutane?
8. Reactions on Fe2+ Mn2+ Fe(OH)2 pale green precipitate
NH4+ with aqueous NaOH Mn(OH)2 pale brown precipitate
NH3 + H2O red litmus paper turns blue from NH3 gas
1/3
