JEE Main 2023 — S Block Elements Question with Solution

A. The order of standard reduction potential (M⁺ | M) for alkali metal ions is Na > Rb > Li. This statement is correct. The standard reduction potential generally increases as we move down the group from Li to Cs so order should be Cs > Rb > K > Na > Li but here Na and K are exception, Na has highest standard reduction potential in the entire group and then K. So right order is Na > K > Cs > Rb > Li. That is why right order is Na > Rb > Li.

Standard reduction potential (M⁺ | M) for alkali metal ions are -

(1). Li = -3.04 V

(2). Na = -2.714 V

(3). K = -2.925 V

(4). Rb = -2.930 V

(5). Cs = -2.927 V

B. CsI is highly soluble in water. This statement is not correct. CsI is the least soluble alkali metal halide in water, and its solubility decreases as the size of the anion increases.

C. Lithium carbonate is highly stable to heat. This statement is not correct. Lithium carbonates decomposes easily on heating to form the lithium oxide and CO₂.

D. Potassium dissolved in concentrated liquid ammonia is blue in colour and paramagnetic. This statement is not correct. In concentrated solution, the blue colour changes to bronze colour and the solution becomes dimagnetic.

E. All the alkali metal hydrides are ionic solids. This statement is correct. All alkali metal hydrides are ionic solids, and their properties are determined by the ionic nature of the compounds.