15. Name the products formed in each case when
a) Hydrochloric acid reacts with caustic soda.
b) Granulated sinc reacts with caustic soda.
c) Carbon dioxide is passed into lime water..
16. What is tooth enamel chemically? State the condition when it starts corroding
when food particles left in mouth after eating degrade? Why do do
tin mouth after eating degrade? Why do doctors suggest use of tooth
powder/toothpaste to prevent tooth decay?
17. What is baking soda chemically called? Give reaction involved in its preparation. Write one of its
passing excess carbon dioxide gas through lime water, it first turns milky and then becomes
colourless. Explain why? Write all the chemical equations of the reactions involved.
19. A) What is universal indicator?
B) Write the chemical equation involved in the preparation of sodium hydroxide. Name the
process
20. A white powder is added while baking breads and cakes to make them soft and fluffy. Write
the name of the powder ? Name its main ingredients. Explain the function of each ingredient.
Write the chemical reaction taking place when the powder is heated during baking.
21. a) Define olfactory indicators. Name two substances which can be used as olfactory indicators
by Choose strong acids from the following: CH3COOH, H2SO4, H2CO3, HNO3
Answers
Answer:
15. a] NaCl
b) sodium zincate and hydrogen
c) calcium carbonate
16. Tooth enamel is mostly hydroxyapatite, which is a mineral form of calcium phosphate. The condition when it starts to corrode is called tooth decay and this happens when the bacteria present in our mouth breaks food particles down into acid with pH less than 5.5 . Doctors suggest the useof tooth paste or powder to prevent the tooth decay, cleaning of the mouth thoroughly after eating with tooth powder/paste, which is basic in nature and neutralizes the excess of acid.
17. Sodium Hydrogen Carbonate.
Reaction involved
Nacl + H₂O +CO₂ + NH₃ ⇒ NH₄Cl + NaHCO₃
Carbon dioxide dissolves in water and slowly reacts with water to produce carbonic acid. The cloudy white solution observed when CO₂ is bubbled into limewater results from a reaction between Ca(OH)₂ and either CO₂ or H2CO3 to form an insoluble calcium carbonate precipitate.
19. A mixture of dyes that changes colour gradually over a range of pH .
b) The process is called chlor alkali process. It is named after the products formed that is chlor for chlorine and alkali for sodium hydroxide.
2NaCl + H₂O ⇒ 2NaOH +Cl₂ + H₂O
20. The white powder is baking Powder. It contains baking soda and mild organic acids.
The reaction Involved is :
2NaHCO₃ ⇒ Na₂CO₃ + H₂O + CO₂
21. a)An Olfactory indicator is a substance whose smell varies depending on whether it is mixed with an acidic or basic solution.
For example vanilla extracts and onion
Strong acids are H₂SO₄ and HNO₃