Science M.C.Q-[Che-1M]

3. Antacid.

Explanation:

Indigestion is caused by the formation of excess acid in the stomach. An antacid is a medicine that is generally a base or a basic salt that neutralises acidity in the stomach.

4. 16mL

Explanation:

It is given that 10mL of a solution of NaOH is completely neutralised by 8mL of a solution of HCl. Hence, 20mL of the solution of NaOH, which is double the amount taken earlier, will require double the solution of HCl taken earlier, i.e., 16mL, to be completely neutralised.

2. HCl

4. 10

Explanation:

A basic solution turns red litmus blue. On the pH scale, bases have values greater than 7, whereas acids have values less than 7. Therefore, the pH of the given solution is likely to be 10.

3. Glass

4. Calcium sulphate, Calcium chloride.

Explanation:

Calcium sulfate (or calcium sulphate) is the inorganic compound with the formula CaSO4 and related hydrates. In the form of γ-anhydrite (the anhydrous form), it is used as a desiccant. One particular hydrate is better known as plaster of Paris, and another occurs naturally as the mineral gypsum

Calcium chloride is an inorganic compound, a salt with the chemical formula CaCl₂. It is a colorless crystalline solid at room temperature, highly soluble in water. Calcium chloride is commonly encountered as a hydrated solid with generic formula CaCl₂ (H₂O)x, where x = 0, 1, 2, 4, and 6. These compounds are mainly used for deicing and dust control. Because the anhydrous salt is hygroscopic, it is used as a desiccant

Hard water can be prepared by dissolving sulphates, chlorides or bicarbonate salts of Ca²⁺ or Mg²⁺ ions.

4. Formation of bubbles of a colourless and odourless gas.

Explanation:

NaHCO₃ + HC₂H₃O₂ → NaC₂H₃O₂ + H₂O + CO₂

There is double displacement in which acetic acid reacts with sodium
bicarbonate to form sodium acetate and carbonic acid.

NaHCO₃ + HC₂H₃O₂ → NaC₂H₃O₂ + H₂CO₃

Carbonic acid is unstable and undergoes a decomposition reaction to produce
carbon dioxide gas.

H₂CO₃ → H₂O + CO₂

Carbon dioxide escapes from the solution as bubbles.

Acetic acid, systematically named ethanoic acid is a colorless liquid organic compound with the chemical formula CH₃COOH (also written as CH₃CO₂H or C₂H₄O₂). When undiluted, it is sometimes called glacial acetic acid. Vinegar is roughly 3 - 9% acetic acid by volume, making acetic acid the main component of vinegar apart from water. Acetic acid has a distinctive sour taste and pungent smell. In addition to household vinegar, it is mainly produced as a precursor to polyvinyl acetate and cellulose acetate. It is classified as a weak acid since it only partially dissociates in solution, but concentrated acetic acid is corrosive and can attack the skin.

1. P and Q.

​​​​​​​​​​​​​​Explanation:

Lather (foam) is formed by the reaction of soap solution with sodium sulphate and potassium sulphate in the test tubes P and Q, respectively. They are dissolved in water to give a neutral solution.

Sulphates, chlorides and bicarbonates of calcium and magnesium make the water hard.

Thus, the lather is not formed in the test tubes R and S.

1. It turns blue litmus red and smells like vinegar.

Explanation:

Since acids turns blue litmus red and acetic acid is a strong acid, so it will turn blue litmus red. Moreover, it smells like that of vinegar.

3. Bubbles of a colourless and odourless gas.

1. A clear and transparent solution is formed.

1. Pungent like vinegar.

Explanation:

Vinegar is no less than 4% acetic acid by volume, making acetic acid the main component of vinegar apart from water. Acetic acid has a distinctive sour taste and pungent smell. Thats why Vapours of acetic acid pungent like vinegar.

3. Dark brown.

2. II, I, IV, III

3. Once - only after completing the experiment.

3. III.

3. Sodium hydroxide.

2. II, V, VI

1. Rain.

Explanation:

Rain water is appropriate for cleansing purpose as rain water is distilled water and which is appropriate for the cleansing purpose. In rain water, micelle formation takes place effectively which is appropriate for cleansing action of soap.

3. CaCl₂; CaSO₄; MgSO₄

​​​​​​​Explanation:

Hard water contains Ca²⁺ and Mg²⁺ ions. So, the salts that can be added to water to make it hard are calcium sulphate, calcium chloride and magnesium chloride.

4. There is a clear, colourless transparent solution in the test-tube.

​​​​​​​Explanation:

Well it is so because Acetic Acid is miscible in water or it is soluble in water, when Acetic acid is added to water it dissolves readily in water forming Homogeneous solution.

4. A and D

Explanation:

The chemical reaction between ethanoic (acetic) acid and sodium carbonate is:

2CH₃COOH + Na₂CO₃ → 2 CH₃COONa + CO₂ + H₂O

On passing CO₂ gas through lime water, the lime water turns milky. The milky appearance of lime water is due to the formation of solid calcium carbonate (CaCO₃).

Reaction:

Ca(OH)₂ + CO₂ → CaCO₃ + H₂O

therefore, out of four test tubes A, B, C and D, only A and D test tubes would be suitable for the correct test of acetic/ ethanoic acid.

Acetic acid also reacts with lime water to give calcium acetate (CH₃COO)₂Ca) as a product. But here it is not considered as a correct test of acetic/ ethanoic acid. 

Reaction:

2 CH₃COOH + Ca(OH)₂ → (CH₃COO)₂Ca + 2H₂O

Hence, the correct answer is the option (d).

1. I and II.

​​​​​​​Explanation:

Saponification reaction  mixture is basic in nature. Formation of soap that is saponification involves base (usually sodium hydroxide, NaOH) hydrolysis of triglycerides, which are esters of fatty acids, to form the sodium salt of a carboxylate. Hence reaction mixture is basic. So, the student will observe that there is no change in the blue litmus paper but red litmus will turn blue.

2. 1, 3 and 6.

​​​​​​​Explanation:

Hard water contains Ca²⁺ and Mg²⁺ ions. So, the salts that can be added to water to make it hard are calcium sulphate, calcium chloride and magnesium chloride.

4. IV, I and II

Explanation:

When acetic acid is added to NaHCO₃ solution, and when a burning splinter is brought near the mouth of each test tube, the splinter would be extinguished due to the evolution of carbon dioxide gas with brisk effervescence from the test tube.

CH₃COOH + NaHCO₃ → CH₃COONa + H₂O + CO₂

4. I, II and IV.

​​​​​​​Explanation:

Sodium hydroxide is in the form of pallets and it readily dissolves in water to form a solution. Since, it is basic in nature, NaOH turns red litmus paper blue.

1. The acetic acid dissolves readily in water.

​​​​​​​Explanation:

Ethanoic acid will readily dissolve in water because both are polar solvents and like dissolves.

4. smells like vinegar and turns blue litmus red.

Explanation:

The odor of vinegar is same as that of acetic acid. Also, being an acid (though weak) it turns blue litmus to red.

3. Bubbles of a colourless and odourless gas.

Explanation:

Acetic acid reacts with Na₂CO₃ to form sodium acetate, carbon dioxide and water. It is this colorless gas carbon dioxide gas which comes out as bubbles.

4. A clear colorless solution.

​​​​​​​Explanation:

It is because reaction of acetic acid CH₃COOH with water H₂O is a simple neutralization reaction because water H₂O acts as base and it will accept proton H⁺ from acetic acid CH₃COOH. Reaction will be like this

CH₃COOH + H₂O ⇒ CH₃COO- + H₃O+

As it is a simple neutralization reaction so the solution will be colorless solution.

3. 2 to 3 hours.

4. All of the above steps.

1. A filter paper.

3. Calcium carbonate.

1. Blue litmus red.

​​​​​​​Explanation:

Under acidic conditions, the phenol is protonated and results in a red color. The process is reversible so if a solution becomes acidic, litmus will be red.  Blue litmus is the deprotonated form and when you put it in acetic acid it will become protonated and turns red.

2. Vinegar.

​​​​​​​Explanation:

Vinegar is no less than 4% acetic acid by volume, making acetic acid the main component of vinegar apart from water. Acetic acid has a distinctive sour taste and pungent smell.

3. Sodium hydrogen carbonate and tartaric acid.

Explanation:

Baking soda is a mixture of sodium hydrogen carbonate (NaHCO₃) and a mild edible tartaric acid.

2. Solution A.

3. Ammonia, Basic

Explanation:

Ammonia is a colourless gas which is made up of nitrogen and hydrogen atoms.

It is produced naturally in the human body and also present in nature, in soil, water, and air.

3. Antacid

2. Baking soda

3. Vanilla essence

Explanation:

An acid base indicator shows a colour change from red to blue or blue to red which is not recognisable by a visually impaired student.

To detect this change, an olfactory indicator is required which gives a particular odour during this colour change.

So vanilla essence is used because of its fruity smell.

3. Vanilla essence.

Explanation: Vanilla works as olfactory indicator, hence it can be used by visually impaired student.

1. Acids

Explanation:

Explanation for correct option:

Acids when dissolves in water hydronium ions (H_3​O⁺) are given out.

Explanation for incorrect options:

(B) Bases when dissolves in water hydroxide ions (OH⁻) are given out.

3. Venus

Explanation:

Atmosphere of venus is made up of thick white and yellowish clouds of sulphuric acid.

3. Sour and change blue litmus to red.

Explanation: Acids have sour taste and can turn blue litmus solution to red.