Chemistry XII chapter 2

Question 2.1: Why alkali and alkaline earth metals are among the reactive elements of the periodic table?

Answer: Alkali and alkaline earth metals are among the reactive elements due to their valence shell electronic configuration. Alkali metals have one valence electron and alkaline earth metal have two valence electrons. Due to large atomic size and low ionization energy, they can lose their valence electrons very easily. It is the reason alkali and alkaline earth metals are very reactive metals in the periodic table.

Question 2.2: Why lime water turns milky with carbon dioxide but becomes clear with excess of CO2:
Answer: When CO2 is passed through lime water it becomes milky due to formation of insoluble calcium carbonate when excess of CO2 is passed then calcium carbonate is converted into calcium bicarbonate that is water soluble, so solution becomes clear.

Question 2.3: how gypsum converted and to plaster of Paris?
Answer: When gypsum is is heated above 100 degree centigrade it loses it's three-quarters of water molecule the product is called plaster of Paris question 2.4 why 2% gypsum is added in US and the cement answer gypsum is an important component of cement it improves setting time of cement and prevents rapid hardening of cement it is the reason that 2% gypsum is added in the cement.

Question 2.4: Why lime is added to the acidic soil?
Answer: lime is very important fertilizer for acidic soils. It is because its basic nature.

Question 2.6: How lime and sand are used to make glass?
Answer: Lime reacts with sand to form calcium silicate. Glass is a mixture of alkali and alkaline earth metals silicates with random structure. Hence, that calcium silicate is the main component of glass, it is the reason that lime and sand are used to make glass.

Question 2.6: How lime water is prepared? Answer: When slaked lime(one part by volume) and sand (3 or 4 volume by parts) are mixed with water, a think paste is formed. It is called lime water.
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Question 2.7: Why lithium carbonate shows easy thermal decomposition but decomposition of potassium carbonate is more difficult.

Answer: Lithium ion has very small ionic size than potassium so in lithium oxide there is strong electrostatic attraction as compared to K2O. Therefore, Lithium oxide has more lattice energy and highly stability it is the reason why lithium carbonate shows easy thermal decomposition and potassium carbonate does not.

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