Water of crystallisation refers to the fixed number of water molecules that are chemically bound within a crystalline compound. These water molecules are integral to the structure of the compound and are typically included in the chemical formula.
Common Name and Chemical Formula of a Commercially Important Compound:
- Common Name: Washing Soda
- Chemical Formula: Na2CO3·10H2_22O
Obtaining Washing Soda: Washing soda is obtained through the Solvay process, which involves the reaction of sodium chloride (salt), ammonia, and carbon dioxide in water. This process yields sodium bicarbonate, which is then heated to produce sodium carbonate. The sodium carbonate is then crystallised from water, incorporating ten molecules of water of crystallisation.
Chemical Equations:
- NaCl + NH3 + CO2 + H2O → NaHCO3 + NH4Cl
- 2NaHCO3 → Na2CO3 + CO2 + H2O
- Na2CO3 + 10H2O → Na2CO3·10H2O
Uses of Washing Soda:
- Water Softening: Washing soda is used to soften hard water by precipitating calcium and magnesium ions.
- Cleaning Agent: It is used in laundry detergents and other cleaning products due to its ability to remove grease, oil, and stains.
Question-Related To Chapters Acid, Base, Salt: Exam Point of View
- To protect tooth decay, we are advised to brush our teeth regularly. The nature of toothpaste used is-
- A compound X in aqueous solution turns red litmus solution blue. Identify ‘X’.
- Which one is a stronger acid, with pH=5 or with pH=2?
- What happens when chlorine is passed over dry slaked lime?
- Dry HCl gas does not change the colour of dry blue litmus paper. Why?
- Fill in the blanks: The chemical formula of plaster of Paris is CaSO4·1/2(H2O)
- Given below are the results of solution tested with universal indicator (pH paper)
- Complete the following reaction- Na₂CO₃ + HCI → 2NaCl + H₂O + CO₂
- Fill the missing data in following table
- Classify these chemicals into strong and weak acid- Hydrochloric acid, Formic acid, nitric acid, acetic acid, Sulphuric acid, citric acid (NCERT Exemplar)
- Name the acid present in ant sting.
- What happens when egg shell is added to nitric acid?
- Name two constituents of baking powder.
- What is the pH of gastric juices released during digestion?
- Which solution is used to dissolve gold? Write its constituents.
- How will you test a gas which is liberated when HCl reacts with an active metal?
- Why does the flow of acid rain water into a river make the survival of aquatic life in the river difficult?
- When concentrated acid is added to water, is the process exothermic or endothermic?
- Which by-product of the chlor-alkali process is used for manufacturing bleaching powder?
- Name one salt which does not have water of crystallisation.
- 15 MCQs Question: Acid, Base, Salt with Answers Class 10: 👉
- Why does bleaching powder smell strongly of chlorine and does not dissolve completely in water?
- Hold one moist and one dry strip of blue litmus paper over dry HCl acid gas. Which strip will turn red and why?
- What is Plaster of Paris? How is it obtained from gypsum?
- What is the role of toothpastes in preventing cavities?
- Explain why sour substances are effective in cleaning copper vessels?
- A white powder is added while baking breads and cakes to make them soft and fluffy. What is the name of the powder? What are its main ingredients?
- How is washing soda prepared from baking soda?
- Though compounds such as glucose and alcohol have hydrogen atoms in their molecules, yet they are not categorized as acids. Why?
- What is the reaction called when an acid reacts with a base to produce salt and water? Give an example also.
- Why are pickles and curd not stored in copper and brass utensils?
- On passing excess CO2 through lime water, it first turns milky and then becomes colourless. Explain why? Write chemical equations.
- How are bases different from alkalis? Are all bases alkalis?
- While constructing a house, a builder selects marble flooring and marble top for kitchen where vinegar and juices of lemon, tamarind etc. are more often used for cooking. Will you agree to this selection and why?
- Indicate with the help of a diagram the variation of pH with change in concentration of H⁺ (aq) and OH⁻ (aq) ions.
- Write the name and formulae of any three hydrated salts.
- Give the equation of reaction between calcium carbonate and hydrochloric acid.
- Why metallic oxides are called basic oxides and non-metallic oxides are called acidic oxides?
- What is pH scale? What is pH value of salt formed by a (a) weak acid and strong base? (b) strong acid and strong base?
- A metal compound ‘A’ reacts with dil H₂SO₄ to produce a gas which extinguishes a burning candle. Identify compound ‘A’ and gas produced. Write a balanced chemical equation for the reaction if one of compound formed is sodium sulphate.
- pH value of salt is 11, which makes Pakoda tasty and crispy. Identify it and write the chemical equation of its formation. Write its two uses also.
- A compound which is prepared by gypsum has the property of hardening when mixed with water. Identify and write its chemical formula. Write the chemical equation for preparation and mention any one use of it.
- Identify the acid and base which form sodium hydrogen carbonate. Write the chemical equation in support of your answer state whether the compound is acidic, basic or neutral. Also write the pH.
- A compound ‘X’ is heated with more con. H₂SO₄ at 443K and produced a Compound ‘Y’. Compound ‘X’ reacts with metal Na and a colourless gas ‘Z’ evolves. Identify ‘X’, ‘Y’ and ‘Z’. Write the equation of chemical reaction takes place with ‘Y’ and also write the role of conc H₂SO₄.
- 2ml of sodium hydroxide solution is added to few pieces of granulated Zn metal taken in test-tube. When the contents are warmed, a gas is evolved which is bubbled through soap solution before testing. Write the equation of chemical reaction involved and test to detect gas. Name the gas which will be evolved when same metal reacts with solution of strong acid.
- What is water of crystallisation? Write the common name and chemical formula of a commercially important compound which has 10. molecules of water. How is this compound obtained? Write its chemical equation also. List any two uses of this compound.
- An element P does not react with dil H₂SO₄ It forms an oxide PO which turns red litmus into blue. P is a metal or a non-metal? Justify your answer.
- What is the chemical name and formula of bleaching powder? What happens when bleching powder is exposed to air for long time? Give any two important uses of bleaching powder.