Acids, Bases and Salts — Science STD 10 — Question

A group of students measured the pH of some substances they found in their homes. Their results are given in the following table:

Sabstance	pH	Sabstance	pH
Apples	3.0	Salt	7.0
Baking soda	8.5	Sugar	7.0
Black coffee	5.0	Toothpaste	9.0
Houshold ammonia	12.0	Vinegar	3.0
Lemon juice	2.5	Washing soda	11.5
Milk	6.0

1. What would the students have used to measure the pH?
2. Which solution is the most acidic?
3. Which solution is the most alkaline?
4. Which solutions are neutral?
5. Which solution can be used to treat wasp stings?
6. Which solution can be used to treat bee stings?

Two metals X and Y form the salts XSO₄ and Y₂SO₄, respectively. The solution of salt XSO₄ is blue in colour whereas that of Y₂SO₄ is colourless. When barium chloride solution is added to XSO₄ solution, then a white precipitate Z is formed alongwith a salt which turns the solution green. And when barium chloride solution is added to Y₂SO₄solution, then the same white precipitate  Z is formed alongwith colourless common salt solution.

1. What could the metals X and Y be?
2. Write the name and formula of salt XSO₄.
3. Write the name and formula of salt Y₂SO₄.
4. What is the name and formula of white precipitate Z?
5. Write the name and formula of the salt which turns the solution green in the first case.

What are alloys? How are they made? Name the constituents and uses of brass, bronze and solder.

Four metals P, Q, R and S are all obtained by the reduction of their oxides with carbon. Metal P is used to form a thin layer over the sheets of metal S to prevent its corrosion. Metal Q is used for electroplating tiffin boxes made of metal S whereas metal R is used in making car batteries. Metals Q and R form an alloy called solder. What are metals P, Q, R and S? How have you arrived at this conclusion?

i. Name a commercially important carbon compound having functional group - OH and write its molecular formula.
ii. Write chemical equation to show its reaction with
1. Sodium metal
2. Excess conc. sulphuric acid
3. Ethanoic acid in the presence of an acid catalyst
4. Acidified potassium dichromate
iii. Also write the name of the product formed in each case.

The white solid compound A decomposes quite rapidly on heating in the presence of a black substance X to form a solid compound B and a gas C. When an aqueous solution of compound B is reacted with silver nitrate solution, then a white precipitate of silver chloride is obtained along with potassium nitrate solution. Gas C does not burn itself but helps burn other things.

1. What is compound A?
2. What is compound B?
3. What is gas C?
4. What do you think is the black substance X? What is its function?
5. What is the general name of substances like X?

A non-metal A which is the largest constituent of air, when heated with H₂in 1:3 ratio in the presence of catalyst (Fe) gives a gas B. On heating with O₂, it gives an oxide C. If this oxide is passed into water in the presence of air, it gives an acid D which acts as a strong oxidizing agent.

1. Identify A, B, C and D.
2. To which group of the periodic table, does this non-metal belongs?

Which among the following are physical or chemical changes?

1. Evaporation of petrol.
2. Burning of Liquefied Petroleum Gas (LPG).
3. Heating of an iron rod to red hot.
4. Curdling of milk.
5. Sublimation of solid ammonium chloride.

Give the reaction for the hydrogenation of unsaturated carbon compounds. Define the term catalyst and name the catalyst used in this reaction. Which oil should be chosen for cooking and why?

State any five physical properties of metals and five physical properties of non-metals.