X and Y are elements of the third period.

X and Y are individually heated in excess chlorine. Each product is purified and then separately added to water, producing two solutions. Both solutions have a pH of less than 5. What could be X and Y

• Na and P

• Mg and Al

• Mg and Si

• Si and P

An ore contains magnesium carbonate and barium carbonate. A sample of the ore is dissolved in nitric acid.

How could this solution be processed into a magnesium compound and a separate barium compound?

• Add HCl _(aq), filter off the solid barium chloride.

• Add HCl _(aq), filter off the solid magnesium chloride.

• Add H₂SO_{4 (aq)}, filter off the solid barium sulphate.

• Add H₂SO_{4 (aq)}, filter off the solid magnesium sulphate.

When calcium and calcium hydride, CaH₂, react separately with water, they each produce a white solid and a colourless gas. The white solid is the same compound in each reaction.

Which statement is correct?

• Both Ca and CaH₂ produce H₂.

• Both Ca and CaH₂ produce O₂.

• Ca produces H₂ and CaH₂ produce O₂.

• Ca produces O₂ and CaH₂ produce H₂.

When concentrated sulfuric acid is added to solid sodium chloride, HCl is formed but not Cl₂.

When concentrated sulfuric acid is added to solid sodium iodide, I₂ is formed. Which statement explains these observations?

• Sulfuric acid is an oxidising agent and chloride ions are more easily oxidized.

• Sulfuric acid is an oxidising agent and iodide ions are more easily oxidized.

• Sulfuric acid is a reducing agent and chloride ions are more easily reduced.

• Sulfuric acid is a reducing agent and iodide ions are more easily reduced.

Elements and their compounds are important as catalyst.

In which process is a compound used, rather than an element?

• catalytic converters

• Contact process

• Haber process

• Hydrogenation of alkenes

The gaseous products of heating a mixture of Ca(OH)₂ and NH₄Cl are passed through solid CaO. This absorbs water vapour and a gas, W, is collected.

A sample of W is oxidized by Cl_2(g) to produce two gases, X and Y. X is an element. Y is acidic. Y reacts with W to produce Z. What are X and Z?

• X is N_{2 ,} Z is CaCl₂

• X is N_{2 ,} Z is NH₄Cl

• X is O_{2 ,} Z is CaCl₂

• X is O_{2 ,} Z is NH₄Cl

Magnesium chloride, MgCl₂, and silicon tetrachloride, SiCl₄, are separately added to water. What are the approximate pH values of the solutions formed?

• MgCl₂ : 0-3 SiCl₄ : 0-3

• MgCl₂ : 0-3 SiCl₄ : 6-7

• MgCl₂ : 6-7 SiCl₄ : 0-3

• MgCl₂ : 6-7 SiCl₄ : 6-7

Cl_2(g) is added to cold, aqueous NaOH. In a separate experiment, Cl_2(g) is added to hot, aqueous NaOH. Which oxidation states of Cl are found in the reactants and products of the two reactions that take place?

• 0, -1, +1 and +5

• 0, -1 and +1 only

• 0, -1 and +5 only

• 0, +1 and +5 only

Ammonia exists as simple covalent molecules, NH₃. Ammonia can react with suitable reagents to form products containing ammonium ions NH₄⁺. Ammonia can also react with suitable reagents to form products containing amide ions, NH₂^-. Which of these nitrogen-containing species are present in an aqueous solution of ammonia?

• ammonia molecules and amides ions only

• ammonia molecules and ammonium ions only

• ammonia molecules only

• ammonium ions only

What would be produced when 60g of NO react with an excess of CO in a catalytic converter?

• 12 g of C and 92 g of NO₂

• 24 g of C and 92 g of NO₂

• 88 g of CO₂ and 28 g of N₂

• 88 g of CO₂ and 56 g of N₂