1.
State what is meant by a pure substance.
[1 mark]
- single element or compound / sharp melting point
JD SCIENCE
C4 Predicting and identifying reactions and products
Indicative marking points. Award marks for equivalent scientific or mathematical wording. Do not issue this sheet with the student worksheet.
2.
State what is meant by a formulation.
[1 mark]
- mixture designed as a useful product
3.
State what is meant by Rf value.
[1 mark]
- distance spot ÷ distance solvent front
4.
State what is meant by chromatography.
[1 mark]
- separating dissolved substances
5.
State what is meant by a flame test.
[1 mark]
- identifies some metal ions by colour
6.
State what is meant by a cation test.
[1 mark]
- sodium hydroxide gives coloured precipitates
7.
State what is meant by an anion test.
[1 mark]
- carbonate, sulfate, halide tests
8.
State what is meant by instrumental analysis.
[1 mark]
- machines such as flame photometers
9.
State what is meant by a melting point.
[1 mark]
- temperature at which a solid becomes liquid
10.
State what is meant by limewater.
[1 mark]
- calcium hydroxide solution
11.
Grace is asked about a pure substance in a OCR Chemistry paper.
(a) [2 marks]
- not a mixture
(b) [3 marks]
- used to check purity
12.
Grace is asked about a formulation in a OCR Chemistry paper.
(a) [2 marks]
- paints, medicines, alloys
(b) [3 marks]
- measured quantities
13.
Grace is asked about Rf value in a OCR Chemistry paper.
(a) [2 marks]
- identifies substances
(b) [3 marks]
- must be 0 to 1
14.
Grace is asked about chromatography in a OCR Chemistry paper.
(a) [2 marks]
- stationary and mobile phases
(b) [3 marks]
- different solubilities
15.
Grace is asked about a flame test in a OCR Chemistry paper.
(a) [2 marks]
- lithium red, sodium yellow, potassium lilac, calcium orange-red, copper green
(b) [3 marks]
- clean wire needed
16.
Grace is asked about a cation test in a OCR Chemistry paper.
(a) [2 marks]
- Cu²⁺ blue, Fe²⁺ green, Fe³⁺ brown
(b) [3 marks]
- add NaOH
17.
Rf = 4.2 / 6.0
[3 marks]
- Final answer: 0.70
18.
A solvent front is 8.0 cm and Rf is 0.25. How far did the spot travel?
[3 marks]
- Final answer: 2.0 cm
19.
How many ions are tested if five flame colours are recorded?
[3 marks]
- Final answer: five metal ions
20.
A solution gives a white ppt with acidified BaCl₂. Which ion?
[3 marks]
- Final answer: sulfate
21.
A solution gives a cream ppt with AgNO₃ that dissolves in concentrated NH₃. Which halide?
[3 marks]
- Final answer: bromide
22.
Percentage purity if 9.6 g of product contains 9.12 g of the pure compound
[3 marks]
- Final answer: 95%
23.
Grace carries out a OCR-style required practical linked to chemical analysis. This is a typical OCR required-practical style question.
(a) [2 marks]
- Independent: the independent variable for this topic
- Dependent: the measured outcome
(b) [2 marks]
- keep all other variables constant
- so the test is fair / only one variable is changed
(c) [2 marks]
- repeat and calculate a mean / use a tighter method
24.
Grace carries out collecting valid data for chemical analysis. This is a typical OCR required-practical style question.
(a) [2 marks]
- Independent: a chosen factor
- Dependent: a quantitative measurement
(b) [2 marks]
- calibrated instrument
- so the test is fair / only one variable is changed
(c) [2 marks]
- systematic error from zero error
25.
Grace carries out drawing a graph for chemical analysis. This is a typical OCR required-practical style question.
(a) [2 marks]
- Independent: x-variable
- Dependent: y-variable
(b) [2 marks]
- same scale / same apparatus
- so the test is fair / only one variable is changed
(c) [2 marks]
- not drawing a line of best fit through the trend
26.
Grace carries out evaluating a method about chemical analysis. This is a typical OCR required-practical style question.
(a) [2 marks]
- Independent: method change
- Dependent: precision / accuracy
(b) [2 marks]
- same sample size
- so the test is fair / only one variable is changed
(c) [2 marks]
- too few repeats
27.
Compare a pure substance with a formulation.
[4 marks]
- single element or compound / sharp melting point
- mixture designed as a useful product
- give one linked difference
28.
Compare a formulation with Rf value.
[4 marks]
- mixture designed as a useful product
- distance spot ÷ distance solvent front
- give one linked difference
29.
Compare Rf value with chromatography.
[4 marks]
- distance spot ÷ distance solvent front
- separating dissolved substances
- give one linked difference
30.
Compare chromatography with a flame test.
[4 marks]
- separating dissolved substances
- identifies some metal ions by colour
- give one linked difference
31.
Apply your knowledge of an anion test to this situation: HCl + limewater; BaCl₂; AgNO₃
[3 marks]
- HCl + limewater; BaCl₂; AgNO₃
32.
Apply your knowledge of instrumental analysis to this situation: faster, more accurate, sensitive
[3 marks]
- faster, more accurate, sensitive