Acids Bases And Salts - MCQ Test (22-11-2017) - Class 10 MCQ

All the above salts contain water of crystallisation and their chemical formulae are given below:
Gypsum - CaSO4.2H₂O - (2 molecules of water of crystallisation) 
Epsom salt- MgSO₄.7H₂O - (7 molecules of water of crystallisation)
Blue vitriol - CuSO₄.5H₂O - (5 molecules of water of crystallisation)
Glauber's salt - Na₂SO₄.10H₂O - (10 molecules of water of crystallisation)

Any compound behaves as a base when it dissociates hydroxide ions (OH^-) in its solution.

A base (NaOH) turns red litmus blue but a netrul compund (water) does not show any colour change.

A basic solution turns red litmus blue and it has pH in-between 8 to 14.
Since (C) and (D) lies in that range, therefore, they will turn blue litmus red.

Phenolphthalein turn pink in colour in basic solutions and soap is basic in nature.

Confirmation of the Nature of the Sample using Red Litmus Paper
To confirm the nature of the sample using red litmus paper, you can follow the steps outlined below:
Step 1: Prepare the Litmus Paper
- Take a strip of red litmus paper.
- Make sure the litmus paper is dry and clean before use.
Step 2: Perform the Test
- Take a small amount of the sample liquid in a clean container.
- Follow the instructions given in the options provided and choose the correct method.
Option A: Dip the litmus paper in a dilute solution of NaOH and then put 2 drops of the liquid sample on it.
- Dip the red litmus paper in a dilute solution of NaOH for a few seconds.
- Remove the litmus paper from the NaOH solution and let it dry for a moment.
- Place two drops of the liquid sample onto the dried red litmus paper.
- Observe any color change that occurs on the litmus paper.
- If the red litmus paper turns blue, it indicates that the sample is acidic.
Option B: Dip the litmus paper in the sample.
- Dip the red litmus paper directly into the liquid sample.
- Observe any color change that occurs on the litmus paper.
- If the red litmus paper turns blue, it indicates that the sample is acidic.
Option C: Put four drops of the liquid sample on the litmus paper.
- Place four drops of the liquid sample directly onto the red litmus paper.
- Observe any color change that occurs on the litmus paper.
- If the red litmus paper turns blue, it indicates that the sample is acidic.
Option D: Dip the litmus paper in a dilute solution of NaCl and then put three drops of the liquid sample on it.
- Dip the red litmus paper in a dilute solution of NaCl for a few seconds.
- Remove the litmus paper from the NaCl solution and let it dry for a moment.
- Place three drops of the liquid sample onto the dried red litmus paper.
- Observe any color change that occurs on the litmus paper.
- If the red litmus paper turns blue, it indicates that the sample is acidic.
Step 3: Analyze the Results
- If the red litmus paper turns blue after following any of the above methods, it confirms that the sample is acidic.
- If the red litmus paper does not change its color, it indicates that the sample is either neutral or basic.
By following the correct method, you can effectively use red litmus paper to confirm the nature of the sample as acidic.

Acids (HCl) reat with metals (Zn) to form salt and release hydrogen gas. The hydrogen gas evolved appears as bubbles.

Formula for bleaching powder is CaOCl₂. It has chlorine available which acts as a disinfectant. It cannot be used as an antacid because it is non-edible. Hans Clever is the most economical method of manufacturing bleaching powder.

Antacids are mild bases,which when given to a person suffering from acidity, neutralises the effect of excess acid produced in the stomach giving relief.

The buds of Petunia act as indicators and change their color in acidic medium.
As the first shower of rain is acidic, therefore the buds of Petunia change their color.

A substance that can react with both acids and bases is called an amphoteric substance.

HCl being an acid turns blue litmus red. 
HCl reacts with zinc metal to evolve hydrogen gas.
HCl reacts with solid sodium carbonate (Na₂CO₃) to evolve carbon dioxide (CO₂) gas.

NaOH is basic in character and higher the pH, stronger is the base.

Sulphuric acid is used in refining of petroleum to remove sulphur and other impurities from it.

Explanation:
On passing CO₂ to lime water for a longer time, the milkiness disappears due to the formation of water-soluble Ca(HCO₃)₂. Let's break down the explanation into bullet points:
- Lime water, also known as calcium hydroxide (Ca(OH)₂), is a clear, colorless solution.
- When carbon dioxide (CO₂) is passed through lime water, a chemical reaction occurs.
- The CO₂ reacts with the calcium hydroxide to form calcium carbonate (CaCO₃), which is insoluble in water.
- The reaction can be represented by the following equation: Ca(OH)₂ + CO₂ → CaCO₃ + H₂O.
- Initially, the formation of calcium carbonate results in the milkiness or turbidity observed in lime water.
- However, if CO₂ is continuously passed through lime water for a longer time, the milkiness eventually disappears.
- This is because the calcium carbonate reacts further with CO₂ to form water-soluble calcium bicarbonate (Ca(HCO₃)₂).
- The reaction can be represented by the following equation: CaCO₃ + CO₂ + H₂O → Ca(HCO₃)₂.
- The formation of water-soluble calcium bicarbonate leads to the disappearance of milkiness and the formation of a clear solution.
Therefore, the correct answer is D: formation of water-soluble Ca(HCO₃)₂.

(C) and (D) are incorrect because the solution of washing soda in water is alkaline which turns red litmus blue. And washing soda is prepared from sodium chloride.

Sulphurous acid is formed on dissolving SO₂ in water.

Triple bonds are the most acidic in nature than other classes of compounds.

Phenolphthalein remains colourless in acidic solution and forms a pink colour in presence of base.

Baking soda (NaHCO₃) is produced by reacting a cold and concentrated solution of sodium chloride(NaCl) with ammonia and carbon dioxide.
NaCl+NH₃+H₂O+CO₂→NaHCO₃+NH₄Cl -(1)
Washing soda (Na₂CO₃.10H₂O) is produced by further heating the NaHCO₃ obtained in first reaction.
2NaHCO₃→Na₂CO₃+CO₂+H₂O
The anhydrous Na₂CO₃ thus obtained is dissolved in water to obtain washing soda.
Na₂CO₃+10H₂O→Na₂CO₃.10H₂O

Distilled water is the purest form of water and it does not contain any acids dissolved in it,so it does not conducts electricity.
Potable water has minute impurities present in it which results in its low conductivity.
​Rain water, on combining with CO₂ gas in the atmosphere produces carbonic acid (H₂CO₃ ) which reacts with to form hydrogen ions,and then conducts electricity.

HCl dissociates into ions in aqueous solutions and shows acidic properties whereas in organic solvents, it does not dissociate completely to show acidic behaviour.

Egg shells contains calcium carbonate. On reaction with HCl they liberate CO₂ gas which turns lime water to milky according to the following equation:
CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂

Both (A) and (D) are correct. Higher the pH, stronger is the base. Basicity of a solution increases from pH value 8 to14.
​Lower the pH, higher is the acidity. Acidity of a solution increases from 6 to 0.

Bases react with non-metallic oxides to form salt and water. This reaction is similar to the neutralisation reaction in which acids react with bases to form salt and water. This shows that non-metallic oxides are acidic in nature.

Human stomach produces gastric juices which contains hydrochloric acid in them resulting in a pH of 1.4. 

Formic acid, also known as methanoic acid, in the bee sting causes itching in the skin..

This is true that alcohols and glucose contain hydrogen ions in them but they do not dissociate to produce hydrogen ions and hence are unable to show acidic behaviour.

It is a white solid, although commercial samples appear yellow. 

Electrolysis of brine solution produces chlorine gas and sodium at
The correct answer is A: Anode, cathode respectively
Explanation:
During the electrolysis of brine solution (sodium chloride solution), the following reactions occur:
1. At the Anode (Positive electrode):
- Chloride ions (Cl-) are oxidized to chlorine gas (Cl2).
- This reaction takes place according to the following half-reaction:
2Cl- → Cl2 + 2e-
2. At the Cathode (Negative electrode):
- Water molecules (H2O) are reduced to hydrogen gas (H2) and hydroxide ions (OH-).
- Simultaneously, the hydroxide ions react with sodium ions (Na+) present in the solution to form sodium hydroxide (NaOH).
- This reaction takes place according to the following half-reactions:
2H2O + 2e- → H2 + 2OH-
Na+ + OH- → NaOH
Therefore, the products of the electrolysis of brine solution are chlorine gas (Cl2) at the anode and sodium hydroxide (NaOH) at the cathode. Sodium metal (Na) is not produced during this process.
To summarize:
- Chlorine gas is produced at the Anode.
- Sodium hydroxide is produced at the Cathode.
Note: The production of sodium metal requires the electrolysis of molten sodium chloride using a different setup.