Use a copy of the Periodic Table where you need one.
Which apparatus should be used to measure out exactly 25.15 cm3 of a salt solution?
Source: Learners' Alley, Experimental Chemistry slides
What is the freezing point of pure water?
Source: Learners' Alley, Experimental Chemistry slides
Gas X is less dense than air and is insoluble in water. Gas Y reacts with acids.
Source: Learners' Alley, Experimental Chemistry slides
A mixture contains W, X, Y and Z. W and X are two immiscible liquids, and X is denser. Y is a solid that is soluble in W but not in X. Z is a solid that is insoluble in both liquids. Outline how you would separate the four substances from each other.
Source: Learners' Alley, Experimental Chemistry slides
Which of the following best describes a pure substance?
Source: 2023 HYSS Sec 3 End-of-Year P1 Q2
The boiling point of water is 100 °C. The melting point of sodium chloride is 800 °C. What is the most likely boiling point of a sample of water that contains a small quantity of sodium chloride?
Source: 2023 HYSS Sec 3 End-of-Year P1 Q3
Mercury is a liquid at 25 °C. What are the melting point and the boiling point of mercury?
| melting point / °C | boiling point / °C | |
|---|---|---|
| A | −39 | 357 |
| B | −22 | −3 |
| C | −8 | 20 |
| D | 30 | 103 |
Source: 2023 HYSS Sec 3 End-of-Year P1 Q4
The solubility of three solids in two solvents, water and methylbenzene, is given in the table. What method is suitable for obtaining P from a mixture of the three solids?
| solid | solubility in water | solubility in methylbenzene |
|---|---|---|
| P | insoluble | insoluble |
| Q | good | insoluble |
| R | insoluble | good |
Source: 2023 HYSS Sec 3 End-of-Year P1 Q5
In the experimental set-up shown below, sulfur dioxide was reacted with oxygen to form sulfur trioxide by passing the mixture through heated platinised asbestos (a substance that speeds up the reaction). What is the function of the concentrated sulfuric acid?
Source: 2023 GESS Sec 3 End-of-Year P1 Q2
Which apparatus is not required in titration experiments?
Source: Broadrick Prelim 2024 P1 Q1
The apparatus below shows the method to collect gas X. Which properties of gas X can be deduced?
Source: 2023 GESS Sec 3 End-of-Year P1 Q3
A mixture contains solid Y mixed with ethanol. Solid Y is insoluble in ethanol. Ethanol has a boiling point of 78 °C and Y has a boiling point of 103 °C. Which of the following apparatus represents the best method used to obtain both solid Y and ethanol?
Source: 2023 GESS Sec 3 End-of-Year P1 Q4
The diagram shows the chromatogram obtained by analysis of a single dye. Which of the following is the correct Rf value of spot B?
Source: 2023 GESS Sec 3 End-of-Year P1 Q6
Aqueous iron(II) sulfate, a pale green solution, is distilled. What is the temperature shown by the thermometer and the colour of the distillate in the conical flask?
| temperature / °C | colour of distillate | |
|---|---|---|
| A | 100 | colourless |
| B | 100 | pale green |
| C | 106 | colourless |
| D | 106 | pale green |
Source: 2024 SMSS Sec 3 End-of-Year P1 Q2
Chromatography can be used to separate and identify components of a mixture. A student wanted to find out whether a sample of black dye is pure. She drew a start line in pencil on a sheet of chromatography paper and placed spots of known dyes A, B, C, D and E and the black dye on the start line. She ran the chromatography using ethanol as the solvent. Fig. 11.1 shows the results.
Source: 2025 CHIJ Sec 4 Prelim P2 Q2
Crude oil is a naturally occurring viscous black oil made up of many hydrocarbons. In oil industries, crude oil is heated and its components turn into vapour. They are then cooled, condensed back into liquids, and collected as different fractions. Each fraction contains different hydrocarbons. Petroleum gases such as propane and butane are collected at the top of the column, where it is coolest.
Source: 2023 GESS Sec 3 End-of-Year P2 A10(a)
A sample of black ink contains a mixture of blue, red and yellow dyes. The solvent used to separate the dyes in black ink is usually a mixture of ethanol and water. The coloured dyes have different Rf values in solvents with different compositions of ethanol, as shown in Fig. 5.1.
Source: Compassvale Sec 4 Exp Prelim 2024 P2 Q5
Bburette[1]
A burette measures to the nearest 0.05 cm3, so it can measure 25.15 cm3.
D273 K[1]
Pure water freezes at 0 °C and temperature in K = temperature in °C + 273.
Water displacement or upward delivery. [1]
Calcium oxide (quicklime). [1]
Gas Y reacts with acids, so it cannot be dried with concentrated sulfuric acid.
Remove the insoluble solid Z from the three other substances by filtration. [1]
From the two immiscible layers, use a separating funnel to run off liquid X, the lower layer. [1]
Separate solid Y from its solution in W by evaporation or crystallisation. [1]
DA yellow solid that melts at 60 °C.[1]
A pure substance has a fixed, sharp melting point.
B104 °C[1]
Dissolved salt raises the boiling point of water a little, so the boiling point is just above 100 °C.
Amelting point −39 °C and boiling point 357 °C[1]
BAdd methylbenzene and stir, then filter, then add the residue to water and stir, and then filter this mixture.[1]
Methylbenzene dissolves R only, so the residue is P and Q. Water then dissolves Q only, so the final residue is pure P.
Bto act as a drying agent[1]
Concentrated sulfuric acid absorbs water, so it dries the gases.
Cmeasuring cylinder[1]
Cless dense than air[1]
The apparatus is upward delivery, so gas X must be less dense than air. There is not enough information to deduce its solubility in water.
Aset-up A[1]
Solid Y is insoluble in ethanol, so filtration separates them easily: Y is the residue and ethanol is the filtrate. The boiling points are distractors.
D0.538[1]
Rf of B = 713 = 0.538
A100 °C and a colourless distillate[1]
Only water boils off, so the thermometer at the side arm reads its boiling point, 100 °C, and the distillate is pure, colourless water.
The black dye is impure because there is more than one spot on the chromatogram. [1]
Determine the boiling point or freezing point of the black dye. [1]
If it boils or freezes at a fixed temperature, it is pure. or If it boils or freezes over a range of temperatures, it is not pure. [1]
Dye B is insoluble in the solvent (ethanol). [1]
Dye A [1]
Distance moved by A = 4.0 − 1.5 = 2.5 cm and distance moved by the solvent front = 7.0 − 1.5 = 5.5 cm. Rf = 2.5 ÷ 5.5 = 0.45 [1]
Fractional distillation [1]
Distillation alone is not accepted.
The components have different boiling points. [1]
No. The components are miscible (they mix). [1]
All the dyes must have different solubilities in the same solvent (the mixture of water and ethanol). [1]
The Rf value of the yellow dye in pure water (0% ethanol) is zero, so the yellow dye is insoluble in pure water. [1]
The Rf value of the red dye in pure ethanol (100% ethanol) is zero, so the red dye is insoluble in pure ethanol. [1]
The black dye would not be completely separated into its components if either pure water or pure ethanol were used. [1]
Percentage of ethanol = 32200 × 100% = 16% [1]
So the Rf value of the blue dye is 0.72. [1]
No, the student cannot conclude that the black dye is pure. [1]
The Rf values of the blue, red and yellow dyes are all 0.4 when the solvent is 80% ethanol, so the three dyes give only one spot. [1]
The start line must be drawn in pencil. [1]
The level of the solvent must be below the start line. [1]