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An alkali metal A gives a compound B (molecular mass = 40) on reacting with water. The compound B gives a soluble compound C on treatment with aluminium oxide. Identify A, B and C and give the reaction involved.

Answer: According to the question, Given x + 16 + 1 = 40 x = 40 - 17 = 23 It is the atomic weight of Na (sodium). Therefore, the... View Article

An element A reacts with water to form a compound B which is used in whitewashing. The compound B on heating forms an oxide C which on treatment with water gives back B. Identify A, B and C and give the reactions involved.

Answer: A is calcium, B is calcium Hydroxide, and C is Calcium Oxide. Ca + 2H2O → Ca(OH)2 + H2 The above reaction is a combination reaction... View Article

Name one metal and one non-metal that exist in a liquid state at room temperature. Also, name two metals having a melting point less than 310 K (37°C)

Answer: The metal which exist as a liquid at room temperature is mercury. Non-metal which exist as a liquid at room temperature is bromine.... View Article

Give two examples each: The metals that are good conductors and poor conductors of heat, respectively.

Answer: Good conductors - Iron and Copper Bad conductors - Lead and Mercury Materials that allow heat to pass through them easily are... View Article

A non-metal A is an important constituent of our food and forms two oxides B and C. Oxide B is toxic whereas C causes global warming (a) Identify A, B and C (b) To which Group of Periodic Table does A belong?

Answer: (a) A is Carbon. B is Carbon monoxide and C is Carbon-dioxide. Carbon compounds are present everywhere i.e. in the food that we eat, the... View Article

What happens when (a) ZnCO3 is heated in the absence of oxygen? (b) a mixture of Cu2O and Cu2S is heated?

Answer: (a) Zinc oxide and carbon dioxide are formed when zinc carbonate is heated in the absence of oxygen. Calcination is the process of... View Article

Give the formulae of the stable binary compounds that would be formed by the combination of the following pairs of elements. (a) Mg and N2 (b) Li and O2 (c) Al and Cl2 (d) K and O2

Answer: Binary compounds are chemical compounds comprising of two distinct elements. An element is a substance that cannot be further divided... View Article

A metal that exists as a liquid at room temperature is obtained by heating its sulphide in the presence of air. Identify the metal and its ore and give the reaction involved.

Answer: Metals low in activity series can be obtained by reducing their sulphides or oxides by heating. At room temperature, mercury is the only... View Article

A metal A, which is used in thermite process, when heated with oxygen gives an oxide B, which is amphoteric in nature. Identify A and B. Write down the reactions of oxide B with HCl and NaOH.

Answer: Metal A is Aluminium and B is Al2O3 Al2O3 with HCl (Hydrochloric acid) Al2O3 + 6HCl → 2AlCl3 + 3H2O Al2O3 with NaOH (Sodium... View Article

What are the constituents of solder alloy? Which property of solder makes it suitable for welding electrical wires?

Answer: Solder is an alloy that is mainly made up of tin and lead. Solder is a fusible metal alloy made up of 60% tin and 40% lead. Lead (Pb)... View Article

The following reaction takes place when the aluminium powder is heated with MnO2 3 MnO2 (s) + 4 Al (s) → 3 Mn (l) + 2 Al2O3 (l) + Heat (a) Is aluminium getting reduced? (b) Is MnO2 getting oxidised?

Answer: (a) No, because aluminium is oxidised as a result of the addition of oxygen. (b) No, manganese is being reduced because it has lost... View Article

A non-metal X exists in two different forms Y and Z. Y is the hardest natural substance, whereas Z is a good conductor of electricity. Identify X, Y and Z.

Answer: X is Carbon. Carbon allotropes include diamond and graphite. Because diamond is the hardest natural substance, Y is a diamond. Graphite... View Article

When a metal X is treated with cold water, it gives a basic salt Y with molecular formula XOH (Molecular mass = 40) and liberates a gas Z which easily catches fire. Identify X, Y and Z and also write the reaction involved.

Answer: X is Na because the molecular mass of NaOH is 40. Na(23) + O(16) → NaOH(40) Hence X is Na Y is NaOH Z is hydrogen has which... View Article

Compound X and aluminium are used to join railway tracks. (a) Identify the compound X (b) Name the reaction (c) Write down its reaction.

Answer: Compound X is Fe2O3. The involved reaction is a thermite reaction which is also called as aluminothermy. Fe2O3(s) + 2Al(s) →... View Article

Generally, when metals are treated with mineral acids, hydrogen gas is liberated, but when metals (except Mn and Mg), treated with HNO3, hydrogen is not liberated, why?

Answer: Because nitric acid is a strong oxidising agent, most metals do not react with it. As a result, when metals other than Mn and Mg are... View Article

Why should the metal sulphides and carbonates be converted to metal oxides in the process of extraction of metal from them?

Answer: Metals are easier to get from their oxides than from their sulphides or carbonates. As a result, metal sulphides and carbonates must... View Article

During the extraction of metals, electrolytic refining is used to obtain pure metals. (a) Which material will be used as anode and cathode for refining of silver metal by this process? (b) Suggest a suitable electrolyte also. (c) In this electrolytic cell, where do we get pure silver after passing electric current?

Answer: Electrolytic refining is the method of using electricity to refine impure metals. In this process, the anode is made of impure metal,... View Article

Iqbal treated a lustrous, divalent element M with sodium hydroxide. He observed the formation of bubbles in a reaction mixture. He made the same observations when this element was treated with hydrochloric acid. Suggest how can he identify the produced gas. Write chemical equations for both the reactions.

Answer: It is a divalent, lustrous element so it is a metal and only very reactive metal can react with NaOH. A base interacts with a metal in... View Article

Which one of the following figures correctly describes the process of electrolytic refining?

Answer: (c) Copper sulphate is used as the cathode in the electrolytic refining of copper, whereas impure copper is used as the anode. The... View Article

Which of the following can undergo a chemical reaction? (a) MgSO4 + Fe (b) ZnSO4 + Fe (c) MgSO4 + Pb (d) CuSO4 + Fe

Answer: (d) CuSO4 + Fe Iron is more reactive than copper hence it displaces copper in the reaction to form FeSO4. Iron displaces copper from its... View Article

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