Chemistry 9202 | Paper 1 Mock 01 | Written Paper 1

Fig. 1 shows a quality-control flow chart for a company making sodium chloride for saline solution. Rock salt is crushed and mixed with water. Insoluble sand is removed, then water is evaporated from the salt solution to obtain crystals. Samples from the final batch are checked by measuring melting range and by testing whether a solution of the crystals leaves a residue after evaporation. The company needs a pure compound because impurities could affect the medical use of the saline solution.

(a) Name the substance that passes through the filter in Fig. 1. [2]
(b) Give the reason why sand can be separated from sodium chloride solution by filtration. [2]
(c) Use particle ideas to describe what happens to water particles when the salt solution is evaporated. [4]
(d) Suggest two tests or observations that would show the final sodium chloride crystals are pure. [4]

Fig. 1 shows electron-shell diagrams prepared for a lesson on noble gases. Table 1 lists the number of electrons in atoms of helium, neon and argon. The teacher asks the class to use the diagrams to predict their chemical behaviour.

(a) Name the group containing neon. [1]
(b) What does the period number tell you about an atom? [1]
(c) Give one reason why argon is unreactive. [1]
(d) Complete the name of the element with 2 electrons: ______. [1]

The table below shows results from a student who added equal-sized pieces of magnesium, calcium and iron to separate samples of dilute acid. Fig. 1 shows the order of these metals in the student’s reactivity series. The volume of hydrogen was measured after 60 s.

(a) What gas is collected in this reaction? [1]
(b) Use Table 1 to name the metal with the fastest reaction. [1]
(c) Complete the word equation: magnesium + acid → magnesium ______ + hydrogen. [1]
(d) Suggest why the pieces of metal were made the same size. [1]

This reaction is used by a water-treatment company to remove ammonia from waste gas. Fig. 1 shows an energy profile for a reaction in which ammonia is oxidised. The products are lower in energy than the reactants.

(a) Name the type of energy change shown. [1]
(b) Give the name for the energy needed to start this reaction. [1]
(c) Use Fig. 1 to describe the energy changes as the reaction takes place. [3]

Fig. 1 shows a student using electrolysis to obtain copper from copper sulfate solution. The table records the mass of each electrode before and after a 20-minute run. The student uses graphite electrodes because graphite is a conductor and does not react easily.

(a) Use Table 1 to give the mass increase of the negative electrode. [1]
(b) Name the metal deposited on the negative electrode. [1]
(c) What particle moves to the negative electrode from the solution? [1]
(d) Give one reason why graphite is used for the electrodes. [1]
(e) Suggest why the negative electrode gains mass. [1]
(f) Complete the formula for copper(II) ions: Cu____. [1]

A student is given a printed inventory for a spacecraft water-recycling unit. The unit uses a small amount of silver compound to reduce microbial growth. Fig. 1 shows a simplified atom model for silver with shells represented by rings. The outer-shell count is not required. The inventory also includes an unknown silver ion detected in the water. The student uses proton and electron numbers to identify its charge.

(a) What is the atomic number of silver? [1]
(b) Give the number of electrons in a neutral silver atom. [1]
(c) Name the particle responsible for the negative charge in an atom. [1]
(d) Use 47 protons and 46 electrons to give the charge on the silver ion. [1]
(e) Complete the ion symbol: Ag___ . [1]
(f) Suggest why the silver ion and silver atom are the same element. [1]

The diagram shows a school laboratory model of ammonia manufacture. Dry nitrogen and dry hydrogen are mixed in the box before being passed over heated iron wool. A student compares the volume of ammonia collected in equal times. Table 1 gives the results when the gas mixture has different nitrogen to hydrogen volume ratios. The gases in the box are measured at the same temperature and pressure.

(a) Complete the word equation: nitrogen + hydrogen ⇌ ______. [1]
(b) Use Table 1 to give the ratio that produced most ammonia. [1]
(c) Name the element in the iron wool that acts as a catalyst. [1]
(d) Suggest why the gases are dried before entering the apparatus. [1]

A student investigates the effect of pressure on an equilibrium mixture for ammonia production using a sealed demonstration chamber. Fig. 1 shows a movable piston compressing nitrogen and hydrogen over an iron catalyst. The chamber is allowed to reach equilibrium before each sample is analysed. Table 1 shows the percentage of ammonia in the final gas mixture. Temperature is kept at 450 °C throughout.

(a) Complete the balanced equation: N₂ + 3H₂ ⇌ ______. [1]
(b) Use Table 1 to state the effect of increasing pressure on ammonia percentage. [1]
(c) Explain this effect using the number of gas molecules in the equation. [2]
(d) Give one disadvantage of using very high pressure in an industrial plant. [1]

Fig. 1 shows a forensic scientist comparing a clear liquid from a damaged battery with a sodium chloride reference solution. Nitric acid and silver nitrate solution are used for both samples.

The battery liquid gives a cream precipitate. The reference gives a white precipitate. The cream precipitate dissolves only slightly in dilute ammonia solution.

(a) Name the halide ion in the battery liquid. [1]
(b) Give the formula of the cream precipitate. [1]
(c) Name the halide ion in the reference solution. [1]
(d) Suggest why nitric acid is used before silver nitrate solution. [1]
(e) Use the ammonia result to support the identification of the cream precipitate. [1]

Table 1 shows tests made on a white powder spilled from a delivery sack at a swimming-pool store. Fig. 1 shows the gas from the acid test being bubbled through limewater.

(a) Name the gas made in the first test. [1]
(b) Name the ion identified in the powder. [1]
(c) Complete the word equation: carbonate + acid → salt + water + ______. [1]
(d) Suggest why the silver nitrate result is useful. [1]
(e) Give the formula of the carbonate ion. [1]

A roadside worker uses solid sodium chloride to help melt ice on a footpath. Fig. 1 shows salt crystals spread over the icy surface.

(a) Name the state of sodium chloride before it dissolves. [1]
(b) Give the name of the mixture formed when sodium chloride dissolves in melted water. [1]
(c) Suggest why salt can make ice melt at a temperature below 0 degrees C. [2]
(d) Give one reason why workers should use only the amount of salt needed. [1]
(e) What happens to the arrangement of water particles when ice becomes liquid water? [1]

Fig. 1 shows a molecular model of iodine. At a coastal laboratory, iodine crystals are warmed gently to make iodine vapour for a test of starch in seaweed samples. The crystals change directly to a purple gas without forming a liquid. The scientist compares this change with melting sodium chloride.

(a) Name the type of bonding between the two iodine atoms. [1]
(b) What is the name of the change from solid iodine directly to gas? [1]
(c) Suggest why iodine has a low melting point compared with sodium chloride. [2]
(d) Give the number of iodine atoms in five iodine molecules. [1]

Fig. 1 shows a model of a water molecule. A water company uses activated carbon to remove some dissolved compounds from drinking water. The chemist reminds a student that water itself is a simple molecular substance, whereas the carbon filter has a giant structure. The water is boiled before a sterile sample is taken.

(a) What is the formula of water? [1]
(b) Name the type of bonding inside a water molecule. [1]
(c) Suggest why boiling water does not break the O-H bonds. [2]
(d) Give one property that makes activated carbon useful in a filter. [1]

The diagram shows a school laboratory flow chart for identifying ions in an unknown white solid. A student dissolves a small mass of the solid in water before splitting the solution between the tests.

The white precipitate dissolves in dilute ammonia. The warmed tube produces ammonia gas.

(a) Name the negative ion identified by the left-hand route. [1]
(b) Name the positive ion identified by the right-hand route. [1]
(c) Give the formula of the unknown compound. [1]
(d) Suggest why the solid is dissolved before testing. [1]
(e) Use the flow chart to name the reagent that is added before silver nitrate. [1]

A coach brings three unlabeled drinks powders to a sports-science laboratory. Powder A is known to contain sodium chloride. Powder B gives a yellow flame and a white precipitate when acidified silver nitrate is added. Powder C gives no flame colour but gives a white precipitate with barium chloride after acidification.

(a) Name the positive ion in powder B. [1]
(b) Name the negative ion in powder B. [1]
(c) Give the formula of the compound in powder B. [1]
(d) Name the negative ion in powder C. [1]

Fig. 1 shows a laboratory test in which chlorine water is shaken with colourless potassium bromide solution. A stopper is fitted before the test tube is shaken. A second tube contains bromine water and potassium chloride solution. The student uses the colour change to compare the reactivity of halogens.

(a) Name the type of reaction taking place when chlorine is added to potassium bromide solution. [1]
(b) Complete the ionic equation.
Cl₂ + 2Br^- → 2Cl^- + ______ [1]
(c) Suggest the colour seen if bromine is formed. [1]
(d) Use the results to state which is more reactive, chlorine or bromine. [2]

Fig. 1 shows a sealed food packet flushed with nitrogen before it is closed. Nitrogen is not a Group 0 element, but the company is considering using argon instead. Both gases reduce the amount of oxygen around the food. The packet contains crisps made with vegetable oil.

(a) Name the Group 0 gas that could be used instead of nitrogen. [1]
(b) Suggest why oxygen is removed from the packet. [1]
(c) Give one property of argon that makes it appropriate for this use. [1]
(d) What name is given to reactions in which a substance combines with oxygen? [2]

Fig. 1 shows a particle model of carbon dioxide released when a carbonate tablet is placed in water. Each circle represents one molecule. A student compares samples containing different numbers of molecules. Avogadro constant is 6.02 × 10²³ molecules per mole. The particle model is not drawn to scale.

(a) Name the element represented by the central atom in each carbon dioxide molecule. [1]
(b) Use the formula CO2 to calculate its Mr. Ar values are C = 12 and O = 16. [2]
(c) Use Avogadro constant to calculate the number of molecules in 0.50 mol of carbon dioxide. [2]
(d) Give the number of oxygen atoms in 0.50 mol of carbon dioxide. [1]