Sara took 2 mL of dilute NaOH solution in a test tube and added two drops of phenolphthalein solution to it. The solution turned pink in colour. She added dilute H₂SO₄ to the above solution drop by drop until the solution in the test tube became colourless. 40 drops of dilute H₂SO₄ were used for the change in colour from pink to colourless. When Sara added a drop of NaOH to the solution, the colour changed back to pink again.
Sara now tried the activity with different volumes of NaOH and recorded her observation in the table given below :

Answer the following questions based on the above information:

(a) If Sara used concentrated H₂SO₄ in place of dilute H₂SO₄, how many drops will be required for the change in colour to be observed?

1. 40
2. < 40
3. > 40

Justify your answer.

(b) Sara measured 20 drops of dil. H₂SO₄ and found its volume to be 1 mL. If Sara observed a change in colour of NaOH solution by using 3 mL of H₂SO₄, how many mL of NaOH did she add to the test tube initially?

OR

Sara takes 10 drops of dilute H₂SO₄ in the test tube and adds two drops of phenolphthalein solution to it. Then she adds NaOH dropwise. Sara observes a change in colour after adding 20 drops of NaOH. What change in colour would she observe and why?

(c) Write a balanced chemical equation for the reaction taking place in the above experiment. Which of the following is true and why? The reaction is a

1. neutralisation and double displacement reaction
2. neutralisation and precipitation reaction
3. precipitation and double displacement reaction
4. neutralisation, double displacement as well as precipitation reaction.

The electronic structures of atoms P and Q are shown below :

Based on the information given above, answer the following questions:

(a) If P and Q combine to form a compound, what type of bond is formed between them?

(b) Give the chemical formula of the compound formed.

(c) The compound so formed is dissolved in water. Is the resultant solution acidic or basic in nature? Justify your answer.

(d) Write the chemical equation for the reaction between ‘Q’ and ethanol.

(e) What will be the formula of the compound formed when ‘P’ undergoes bonding with carbon?

A hydrocarbon with the formula C_xH_y undergoes complete combustion as shown in the following equation:

2C_xH_y + 9O₂ → 6CO₂ + 6H₂O

(a) What are the values of ‘x’ and ‘y’?

(b) Give the chemical (IUPAC) name of the hydrocarbon.

(c) Is C_xH_y a saturated or an unsaturated hydrocarbon?

(d) Name the alcohol which on heating with conc. H₂SO₄ will produce the above hydrocarbon C_xH_y.

(e) Write a balanced chemical equation for the reaction of C_xH_y with hydrogen gas in presence of Nickel.