Author: Dr. Vikas Jasrotia

s block elements – Important Questions & Answers s block elements Que 1. Why are alkali metals not found in nature? Ans 1. Due to high chemical reactivity alkali metals do not occur free in nature. They are found in the earth’s crust in the form of halide, sulphate, carbonate, silicate, borate, oxide ores, etc Que 2. Why are halides of beryllium polymeric? Ans 2. The halides of Be are electron deficient as their octets are incomplete. Therefore, to complete their octets, the halides polymerize. Que 3. Arrange the alkaline earth metal carbonates in the decreasing order of thermal stability.…

Que. Discuss the various reactions involved in the Solvay process. Ans. In the Solvay process. When carbon dioxide is passed through a concentrated solution of brine saturated with NH3, NaHCO3 gets precipitated. NaHCO3 on subsequent heating gives Na2CO3. NaCl + NH3 + CO2 + H2O → NaHCO3 + NH4Cl 2 NaHCO3 → Na2CO3 + CO2 + H2O CO2 needed for the reaction is prepared by heating calcium carbonate and the quick lime, CaO is dissolved in water to form slaked lime, Ca(OH)2 CaCO3 → CaO + CO2 CaO + H2O → Ca(OH)2 NH3 needed for the purpose is prepared…

Que. An element occupies group number 1 and period number 3. This element heated in the air gives compound A. With water, it gives compound B which is a strong base. The reaction of B with ammonia gives compound C, which is used as a reducing agent in organic chemistry. Identify the element A, B, and C. Ans. (i) As per the position in the periodic table this element occupying group number 1 and period number 3 is sodium. (ii) When Sodium is heated in air, it forms sodium peroxide (A) 4Na + O2 → 2 Na2O2 (iii) With water,…

Que. What is entropy? Why is the entropy of a substance taken as zero at 0 K? Calculate the ΔG for the reaction? N2(g) + 3 H2(g) → 2 NH3(g) at 298K The value of equilibrium constant (K) is 6.6 × 105, R = 8.314 JK-1mol-1. Ans. It is measure of randomness or disorder of system. Because at 0K there is complete order in the system. ΔG0 = – 2.303 RT log K = – 2.303 × 8.314 × 298 × log 6.6 × 105 = – 5705.8 [log 6.6 + log 105] = – 5705.8 [0.8195 + 5.0] =…

(Solutions) Chemical Kinetics Class 12 Test – 1 Chemical Kinetics Class 12 Ans 1. (B) Rate is inversely proportional to the surface coverage Ans 2. (A). V0 ∝ a Vt ∝ a + x Vt – V0 ∝ (a + x – a) 2V0 – Vt ∝ a – x   Ans 3.  (B). The rate law for the dimerization of NO2 is   The temperature will change the value of the specific rate constant. Ans 4. (C). According to the Arrhenius equation, a straight line is to be obtained by plotting the logarithm of the rate constant of a chemical reaction…

Chemical Kinetics Class 12 Test – 1 Chemical Kinetics Que 1. The decomposition of phosphine (PH3) on tungsten at low pressure is a first-order reaction. It is because the (A) Rate is proportional to the surface coverage (B) Rate is inversely proportional to the surface coverage (C) Rate is independent of the surface coverage (D) Rate of decomposition is very slow Que 2. For the first-order reaction, A (g) → B (g) + C (g) + D (s) taking place at constant pressure and temperature condition. Initially, the volume of the container containing only A was found to be V0 and after…

Answers Electrochemistry Important Questions – Class 12 Answers Electrochemistry Important Questions Ans 1. Cell stops working after some time because the electrode potential of both the electrodes becomes equal. Ans 2. Ammonium Chloride (NH4Cl) Ans 3. During the charging of lead storage batteries, it acts as an electrolytic cell and during the discharging of the lead storage battery, it acts as a galvanic cell. During the charging of the lead storage battery, the reactions get reversed and the cathode becomes the anode and the anode becomes the cathode. Ans 4. A dry cell becomes dead after a long time even if…

Electrochemistry Important Questions – Class 12  Electrochemistry Important Questions Que 1. Why does a cell stop working after some time? Que 2. What is the electrolyte used in a dry cell? Que 3. Why can a lead storage cell be recharged? Que 4. Why does a dry cell become dead after a long time even if it has not been used? Que 5. Mention the reaction occurring at (i) anode and (ii) cathode during the working of mercury cell. Que 6. Name any two metals which can be used for the cathodic protection of iron? Que 7. Why is it…

(Answers) Class 10 Chemical Reactions and Equations Test – 1 (Answers) Class 10 Chemical Reactions and Equations Ans 1. The word equation for the reaction is: Iron + Water → Ferric oxide + Hydrogen The symbol equation for the same reaction is: Fe + H2O → Fe2O3 + H2 ­ The balancing of the equation is done in the following steps: Step I. Let us count the number of atoms of all the elements in the reactants and products on both sides of the equation. Element No. of atoms of reactants (L.H.S.) No. of atoms of products (R.H.S.) Fe 1…

Class 10 Chemical Reactions and Equations Test – 1 Class 10 Chemical Reactions and Equations Que 1. Write a balanced chemical equation for the following (using different steps) (i) Iron reacts with water (steam) to form the ferric oxide and liberate hydrogen gas. (ii) When potassium chlorate (KClO3) is heated in the presence of a manganese dioxide catalyst, it decomposes to form potassium chloride and oxygen gas. Que 2. Identify the following reaction type in which: (i) Carbon monoxide reacts with oxygen to form carbon dioxide (ii) Ferrous sulphate is heated strongly Que 3. When an electric current is passed…