Valence, oxidation states and chemical reactivity
- Which of the following statements are NOT correct?A. Hydrogen is used to reduce heavy metal oxides to metals.B. Heavy water is used to study reaction mechanism.C. Hydrogen is used to make saturated fats from oils.D. The H-H bond dissociation enthalpy… Answer: 4. D, E only Key idea: Check each statement. A. True: H₂ reduces oxides of less active (heavy) metals. B. True: D₂O is used as a tra... 1
- In which one of the following arrangements the given sequence is not strictly according to the properties indicated against it ? Answer: 2. H₂O < H₂S < H₂Se < H₂Te : Increasing pK_a values Key idea: check each trend. 1: acidic strength HF < HCl < HBr < HI is correct (w... 1
- Statement I : Acid strength increases in the order given as HF << HCl << HBr << HI.Statement II : As the size of the elements F, Cl, Br, I increases down the group, the bond strength of HF, HCl, HBr and HI decreases and so the acid strength increases… Answer: 1. Both Statement I and Statement II are true. Key idea: acid strength of hydrogen halides depends on the H-X bond strength. Down th... 1
- Match the following :Oxide | Nature(a) CO (i) Basic(b) BaO (ii) Neutral(c) Al_2O_3 (iii) Acidic(d) Cl_2O_7 (iv) AmphotericWhich of the following is correct option ? Answer: 2. (a)-(ii), (b)-(i), (c)-(iv), (d)-(iii) CO: neutral oxide (a)-(ii). BaO: basic oxide of an s-block metal (b)-(i). Al₂O₃ : amphoter... 1
- The following metal ion activates many enzymes, participates in the oxidation of glucose to produce ATP and with Na, is responsible for the transmission of nerve signals. Answer: 4. Potassium Potassium ions activate many enzymes, take part in oxidation of glucose to give ATP, and together with sodium ions carr... 1
- Which of the following is an amphoteric hydroxide ? Answer: 4. Be(OH) ₂ Going down group 2, hydroxides become more basic. Sr(OH)₂ , Ca(OH)₂ and Mg(OH)₂ are basic. Be(OH)₂ dissolves in both aci... 1
- The method used to remove temporary hardness of water is : Answer: 2. Clark's method Key idea: temporary hardness is due to bicarbonates of Ca and Mg, and the method meant specifically for it is Clar... 1
- Enzymes that utilize ATP in phosphate transfer require an alkaline earth metal (M) as the cofactor. M is : Answer: 2. Mg ATP-utilising enzymes (phosphate transfer) need mathrmMg²⁺ as cofactor; Mg binds the phosphate groups of ATP. Ca is mainly inv... 1
- Which of the following oxides is most acidic in nature ? Answer: 3. BeO Acidic character of oxides falls as the metallic character of the element rises. In group 2, MgO, CaO and BaO are basic (basi... 1