Free Reactions of Group II Elements MCQs with Answers

1. Group II elements are called alkaline earth metals and, compared with group I, they are

• A. less reactive, with higher melting points and harder solids
• B. more reactive in every case
• C. non metallic in character
• D. monovalent in their compounds

Explanation: Group II atoms are smaller and must lose two electrons rather than one, so more energy is needed and they are less reactive than their group I neighbours. Having two delocalised electrons per atom also gives stronger metallic bonding, hence higher melting points and greater hardness. They are divalent, forming ions with a charge of plus 2.

2. The thermal stability of the group II carbonates from magnesium to barium

• A. decreases down the group
• B. is the same for all
• C. increases down the group
• D. first increases then decreases

Explanation: A small, highly charged cation polarises the carbonate ion strongly and weakens the carbon to oxygen bonds, so magnesium carbonate decomposes at a relatively low temperature while barium carbonate needs a much higher one. Polarising power falls as the cation gets larger down the group, so stability rises. The nitrates and hydroxides follow the same pattern for the same reason.

3. Which of the following group II compounds is used in medicine as an antacid?

• A. Barium sulphate
• B. Magnesium hydroxide
• C. Calcium carbide
• D. Beryllium chloride

Explanation: Magnesium hydroxide, sold as milk of magnesia, is a weak insoluble base that neutralises excess stomach acid without being absorbed in quantity. Barium sulphate is also used medically but as a contrast medium for X rays, and it is safe only because it is so insoluble that the toxic barium ions are not released. Beryllium compounds are highly toxic.

4. When calcium reacts with cold water, the products are

• A. calcium oxide and hydrogen
• B. calcium hydride and oxygen
• C. calcium hydroxide and hydrogen
• D. calcium carbonate and hydrogen

Explanation: Calcium reacts steadily with cold water to give a suspension of slightly soluble calcium hydroxide, known as limewater when filtered, together with bubbles of hydrogen. Magnesium reacts only very slowly with cold water but readily with steam, which gives the oxide instead. Calcium carbonate would require carbon dioxide to be present.

5. Which property increases down group II from beryllium to barium?

• A. First ionisation energy
• B. Electronegativity
• C. Solubility of the hydroxides in water
• D. Melting point of the metal

Explanation: Hydroxide solubility rises down the group, so magnesium hydroxide is only sparingly soluble while barium hydroxide dissolves appreciably, whereas the sulphates show the opposite trend and become less soluble. Ionisation energy and electronegativity both fall down a group as the atoms get larger. This contrast between hydroxides and sulphates is a favourite examination point.