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Name the substance which on treatment with chlorine yields bleaching powder

Answer: Calcium hydroxide is the material that produces bleaching powder when introduced to chlorine. The chemical name of bleaching powder is... View Article

Do basic solutions also have H⁺(aq) ions? If yes, then why are these basic?

Answer: Bases are substances to release hydroxide ions (OH– ions) when dissolved in water. They are found to have a soapy texture when... View Article

What effect does the concentration of H⁺(aq) ions have on the nature of the solution?

Answer: The nature of the solution is determined by the concentration of hydrogen ions. If the concentration of hydrogen ions in a solution... View Article

You have two solutions, A and B. The pH of solution A is 6 and pH of solution B is 8. Which solution has more hydrogen ion concentration? Which of this is acidic and which one is basic?

Answer: pH is defined as the negative logarithm of H+ ion concentration. Hence, the meaning of the name pH is justified as the power of hydrogen.... View Article

How is the concentration of hydroxide ions (OH^–) affected when excess base is dissolved in a solution of sodium hydroxide?

Answer: When a base is dissolved in sodium hydroxide solution, the number of hydroxide ions increases, but it eventually reaches saturation. And... View Article

How is the concentration of hydronium ions (H₃O⁺) affected when a solution of an acid is diluted?

Answer: As acid is added to water, a certain amount of hydronium will be present in a certain volume of solution. As we dilute a solution, the... View Article

While diluting an acid, why is it recommended that the acid should be added to water and not water to the acid?

Answer: The reaction of acid and water is an exothermic reaction since a lot of heat is liberated during the reaction. This heat changes some... View Article

Why does dry HCl gas not change the colour of the dry litmus paper?

Answer: It does not dissociate into H+ ions when dry HCL is used. Only in aqueous solution can acids dissociate into ions. Since HCL is not... View Article

Why do HCl, HNO₃, etc., show acidic characters in aqueous solutions while solutions of compounds like alcohol and glucose do not show acidic character?

Answer: Acids are substances that produce hydrogen ions as they dissociate with water. As some compounds dissociate in aqueous solution, hydrogen... View Article

Which gas is usually liberated when an acid reacts with a metal? Illustrate with an example. How will you test for the presence of this gas?

Answer: As acid reacts with metal, hydrogen gas is released. A formation of gas bubbles has been observed along the metal's surface. The bubbles... View Article

Oil and Fat containing food items are flushed with Nitrogen. Why?

Answer: The main objective of flushing Nitrogen into food packets containing oil and fat products is to avoid rancidity, which results when the... View Article

A shiny brown coloured element ‘X’ on heating in the air becomes black in colour. Name the element ‘X’ and the black coloured compound formed.

Answer: copper The shiny brown coloured element is Copper metal. As copper is heated in the air, it reacts with oxygen in the air to form black... View Article

Explain the following in terms of gain of oxygen with two examples each. (a) Oxidation (b) Reduction

Answer: Oxidation and reduction reactions are two chemical reactions that often occur together. There is an electron exchange in this reaction.... View Article

In the refining of Silver, the recovery of silver from Silver nitrate solution involves displacement reaction by Copper metal. Write down the reaction involved.

Answer: Cu(s) + 2AgNO3(aq) → Cu(NO3)2(aq) + 2Ag(s) The type of reaction is a displacement reaction. A displacement reaction is one wherein... View Article

What is meant by exothermic and endothermic reactions? Give examples.

Answer: In a chemical reaction, energy is used for breaking the bonds of the reactants also energy is used in formation of new bonds. So, there... View Article

Write a balanced chemical equation for the following and identify the type of reaction of each case KBr + BaI² → KI + BaBr² ZnCO³ → ZnO + CO² H²+ Cl → HCl Mg + HCl → MgCl² + H²

Answer: The representation of a chemical reaction in the form of substances is known as a chemical equation. The equation in which the number of... View Article

Translate the following statements into chemical equations and balance them. (a) Hydrogen gas combines with nitrogen to form ammonia. (b) Hydrogen sulphide gas burns in air to give water and sulphur dioxide. (c) Barium chloride reacts with aluminium sulphate to give Aluminium chloride and a precipitate of barium sulphate. (d) Potassium metal reacts with water to give potassium hydroxide and Hydrogen gas.

Answer: The representation of a chemical reaction in the form of substances is known as a chemical equation. The equation in which the number of... View Article

What happens when dilute hydrochloric acid is added to iron fillings? Tick the correct answer. (1) Hydrogen gas and Iron chloride are produced. (2) Chlorine gas and Iron hydroxide are produced. (3) No reaction takes place. (4) Iron salt and water are produced.

Answer: (1) Hydrogen gas and iron chloride are produced. Let us consider the reaction between acid and metal Acid + Metal → Salt + Hydrogen... View Article

Which of the statements about the reaction below are incorrect? 2PbO(s) + C(s) → 2Pb(s) + CO2(g) (a) Lead is getting reduced (b) Carbon Dioxide is getting oxidised (c) Carbon is getting oxidised (d) Lead oxide is getting reduced (i) (a) and (b) (ii) (a) and (c) (iii) (a), (b) and (c) (iv) all

Answer: (i) (a) and (b) 2PbO(s) + C(s) → 2Pb(s) + CO2(g) Reduced substance - Pb Pb2+ + 2e- → Pb Pb gains electrons or its oxidation number... View Article

Identify the substances that are oxidized and that are reduced in the following equation. (i) 4Na(s) + O₂(g) → 2Na₂O(s) (ii) CuO(s) + H₂(g) → Cu(s) + H₂O(l)

Answer: The oxidized substance is called a reduction agent. The reduced substance is called an oxidizing agent. (i) 4Na(s) + O2(g) →... View Article

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