Answers of Unsolved worksheet Q 4

4. Unsolved question.. Previous One:-

Mention the type of chemical reaction that takes place when:
(i) a magnesium ribbon is burnt in air.- Combination Reaction
(ii) limestone is heated.- Thermal decomposition
(iii) silver bromide is exposed to sunlight.- Photo Decomposition
(iv) electricity is passed through acidified water.- Electric Decomposition
(v) ammonia and hydrogen chloride are mixed with each other.- Combination
Write the chemical equation for each reaction

Complete Answers:

i) Combination reaction: $2 M g + O_{2} \to 2 M g O$

ii) Thermal Decomposition reaction: $C a C O_{3} \to C a O + C O_{2}$

iii) Photo Decomposition reaction: $2 A g B r \to 2 A g + B r_{2}$

iv) Electric Decomposition reaction: $2 H_{2} O \to 2 H_{2} + O_{2}$

v) Combination reaction: $N H_{3} + H C l \to N H_{4} C l$
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Worksheet 3

Acid-Base and Salt 1. How is concentration of hydronium ions (H3O+) affected when a solution of acid isdiluted? Ans. The concentration of hydronium ions decreased when the solution of an acid is diluted. 2. What effect does the concentration of H+ ions have on the nature of the solution? Ans. Higher the concentration of H+ ions, greater is the acidic nature of the solution. 3. Name the substance which on treatment with chlorine yields bleaching powder. Ans. Slaked lime or calcium hydroxide. 4. What is the common name of the compound CaOCl2? Ans. Bleaching powder. 5. Name the sodium compound which is used for softening hard water Ans. Sodium carbonate is used for softening hard water.

100 % Success Class X Board based most important question

Chemical Reaction And Chemical Equation 1. A compound ‘A’ is used in the manufacture of cement. When dissolved in water, it evolves a large amount of heat and forms compound ‘B’. (i) Identify A and B. (ii) Write chemical equation for the reaction of A with water. (iii) List two types of reaction in which this reaction may be classified. (2020) Answer: (i) A is calcium oxide, CaO which is used in the manufacturing of cement. B is calcium hydroxide Ca(OH) 3 . (iii) The given reaction is a combination reaction. Example : NH 3(g) (g) + HCl (g) → NH 4 Cl (s) 2. Mention with reason the colour changes observe when: (i) silver chloride is exposed to sunlight. (ii) copper powder is strongly heated in the presence of oxygen. (iii) a piece of zinc is dropped in copper sulphate solution. Ans: (i) When white silver chloride is left exposed to sunlight, its colour changes to grey as it decomposes to silver in the presence of sunlight. This type of reaction is called photodeco...

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