When an acid reacts with a metal, hydrogen gas is usually released.
Example:
When zinc (Zn) reacts with hydrochloric acid (HCl):
Zn + 2HCl → ZnCl₂ + H₂ (gas)
Test for hydrogen gas: -Bring a burning matchstick near the mouth of the test tube. If hydrogen gas is present, it will burn with a ‘pop’ sound.
More Questions on Acids, Bases and Salts
Name and describe giving chemical equation the process used for producing sodium hydroxide. Why is this process so named?
→ 2Write chemical names and formulae of plaster of Paris and Gypsum.
→ 3Write the chemical formula of hydrated copper sulphate and anhydrous copper sulphate. Giving an activity illustrate how these two are interconvertible.
→ 4How is plaster of Paris prepared? What reaction takes place when it sets to a hard mass?
→ 5What are anhydrous and hydrated salts? Explain with a suitable example of each.
→ 6A student dropped a few pieces of marble in dilute hydrochloric acid contained in a test tube. The evolved gas was passed through lime water. What change would be observed in lime water? Write balanced chemical equations for both the changes observed.
→ 7Define water of crystallisation. Give the chemical formula for two compounds as examples. How can it be proved that the water of crystallisation makes a difference in the state and colour of the compounds?
→ 8If someone in the family is suffering from a problem of acidity after overeating, which of the following substances would you suggest as a remedy?
→ 9Define an acid-base indicator. Mention one synthetic acid-base indicator.
→ 10A white powder is added while baking cakes to make it soft and spongy. Name its main ingredients. Explain the function of each ingredient. Write the chemical reaction taking place when the powder is heated during baking.
→ 11Identify the acid and the base from which sodium chloride is obtained. Which type of salt is it? When is it called rock salt? How is rock salt formed?
→ 12Why does an aqueous solution of an acid conduct electricity ?
→ 13Why do HCl, HNO3, etc show acidic characters in aqueous solutions while solutions of compounds like alcohol and glucose do not show acidic character ?
→ 14Why should curd and sour substances not be kept in brass and copper vessels ?
→ 15You have been provided with three test tubes. One of them contains distilled water and the other two contain an acidic solution and a basic solution, respectively. If you are given only red litmus paper, how will you identify the contents of each test tube ?
→ 16Blue litmus paper is dipped in a solution. It remains blue. What is the nature of the solution? Explain.
→ 17Three liquids are given to you. One is hydrochloric acid, another is sodium hydroxide and third is a sugar solution. How will you identify them? You have only turmeric indicator.
→ 18Explain why: (a) An antacid tablet is taken when you suffer from acidity (b) Calamine solution is applied on the skin when an ant bites. (c) Factory waste is neutralised before disposing it into the water bodies.
→ 19Dorji has a few bottles of soft drink in his restaurant. But, unfortunately, these are not labelled. He has to serve the drinks on the demand of customers. One customer wants acidic drink, another wants basic and third one wants neutral drink. How will Dorji decide which drink is to be served to whom?
→ 20Describe the process of neutralisation with the help of an example.
→ 21Is the distilled water acidic/basic/neutral? How would you verify it?
→ 22Name the source from which litmus solution is obtained. What is the use of this solution?
→ 23Ammonia is found in many household products, such as window cleaners. It turns red litmus blue. What is its nature?
→ 24State differences between acids and bases.
→ 25Write the names of the product formed when zinc reacts with NaOH. Also write the balanced chemical equation for the reaction involved. Write a test to confirm the presence of the gas evolved during this reaction.
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