SECTION - A
Select and write one most appropriate option out of the four options given for each of the questions 1 - 20:
In the experimental setup given below, it is observed that on passing the gas produced in the reaction in the solution 'X' the solution 'X' first turns milky and then colourless.
The option that justifies the above stated observation is that 'X' is aqueous calcium hydroxide and
[1 mark]
SECTION - A
Select and write one most appropriate option out of the four options given for each of the questions 1 - 20:
The table below has information regarding pH and the nature (acidic/basic) of four different solutions. Which one of the options in the table is correct?
| Option | Solution | Colour of pH paper | Approximate pH value | Nature of solution |
|---|---|---|---|---|
| (a) | Lemon juice | Orange | 3 | Basic |
| (b) | Milk of magnesia | Blue | 10 | Basic |
| (c) | Gastric juice | Red | 6 | Acidic |
| (d) | Pure water | Yellow | 7 | Neutral |
[1 mark]
Select washing soda from the following:
[1 mark]
SECTION - B
Q. No. 21 to 26 are very short answer questions.
(a) (i) A compound 'X' which is prepared from gypsum has the property of hardening when mixed with proper quantity of water. Identify 'X' and write its chemical formula.
(ii) State the difference in chemical composition between baking soda and baking powder.
OR
(b) Write balanced chemical equation for the reaction that occurs when:
(i) blue coloured copper sulphate crystals are heated and
(ii) Sodium hydrogen carbonate is heated during cooking.
[2 marks]
SECTION - C
Q. No. 27 to 33 are short answer questions.
(a) Suggest one remedial measure each to counteract the change in pH in human beings in following cases:
(i) Production of too much acid in stomach during indigestion
(ii) Stung by a honey bee / nettle leaves
(b) Fresh milk has a pH of 6. When it changes into curd will its pH increase or decrease? Why?
[3 marks]