Acids, Bases and Salts: Class 10 Science Q&A · Page 3
77 free answers on Acids, Bases and Salts (Science) for Class 10 students, across CBSE, ICSE and State boards.
Question & Answer
Questions
- ScienceClass 10CBSE
During the preparation of hydrogen chloride gas on a humid day, the gas is usually passed through the guard tube containing calcium chloride. The role of calcium chloride taken in the guard tube is to (a) absorb the evolved gas (b) moisten the gas (c) absorb moisture from the gas (d) absorb Cl– ions from the evolved gas
Soln: Answer is (c) absorb moisture from the gas Explanation: Calcium is a good dehydrating agent. It has property to absorb moisture. Hence it is used as a desiccant to dry gases and Hydrocarbons in the industries.
- ScienceClass 10CBSE
An aqueous solution turns red litmus solution blue. Excess addition of which of the following solution would reverse the change? (a) Baking powder (b) Lime (c) Ammonium hydroxide solution Hydrochloric acid
Soln: Answer is (d) Hydrochloric acid Explanation: If the solution turns red litmus to blue color then the solution should be basic in nature. Its effect can be neutralized by adding an acid hence (d) Hydrochloric acid is the answer.
- ScienceClass 10CBSE
What happens when a solution of an acid is mixed with a solution of a base in a test tube? (i) The temperature of the solution increases (ii) The temperature of the solution decreases (iii) The temperature of the solution remains the same (iv) Salt formation takes place (a) (i) only (b) (i) and (iii) (c) (ii) and (iii) (i) and (iv)
Soln: Answer is (d) (i) and (iv) Explanation: When acid is mixed with a solution of base it results in neutralization reaction. Neutralization is an exothermic reaction which result in the formation salt.
- ScienceClass 10CBSE
Give two important uses of washing soda and baking soda.
Washing soda Baking soda 1. It is used as an electrolyte 1. It can be used to test the garden soil for acidity. If bubbles are developed, then the soil is too acidic 2. It can be used domestically as a water softener for laundry. 2
- ScienceClass 10CBSE
What is a neutralisation reaction? Give two examples.
The reaction of the acid + base gives a product of salt + water, which is considered a neutralisation reaction. Examples: NaOH + HCl → NaCl + H2O Mg(OH)2 + H2CO3 → MgCO3 + 2H2O
- ScienceClass 10CBSE
Plaster of Paris should be stored in a moisture-proof container. Explain why.
Solution: Plaster of Paris should be stored in a moisture-proof container because moisture can affect the Plaster of Paris by slowing down the setting of the plaster because of hydration. This will turn plaster useless.
- ScienceClass 10CBSE
A milkman adds a very small amount of baking soda to fresh milk. (a) Why does he shift the pH of the fresh milk from 6 to slightly alkaline? (b) Why does this milk take a long time to set as curd?
(a) He shifted the pH of the fresh milk from 6 to slightly alkaline to prevent milk from getting sour due to the production of lactic acid. (b) This milk takes a long time to set into curd because the lactic acid produced here first neutralises the pH, and then the pH is reduced to turn the milk into curd.
- ScienceClass 10CBSE
Fresh milk has a pH of 6. How do you think the pH will change as it turns into curd? Explain your answer.
Solution: Fresh milk is turned to curd due to the production of lactic acid. Lactic acid reduces the pH of the milk.
- ScienceClass 10CBSE
Equal lengths of magnesium ribbons are taken in test tubes A and B. Hydrochloric acid (HCl) is added to test tube A, while acetic acid (CH3COOH) is added to test tube B. Amount and concentration taken for both the acids are the same. In which test tube will the fizzing occur more vigorously and why?
HCl is a strong acid, whereas acetic is a weaker acid. Fizzing occurs because of the production of the hydrogen gas obtained due to the reaction of the acid on the magnesium ribbon. Since HCl is a very strong acid, there is a lot of liberation of hydrogen gas from test tube A. Therefore, more fizzing takes place in test tube A.
- ScienceClass 10CBSE
Five solutions, A, B, C, D and E, when tested with a universal indicator, showed pH as 4, 1, 11, 7 and 9, respectively. Which solution is (a) Neutral? (b) Strongly alkaline? (c) Strongly acidic? (d) Weakly acidic? (e) Weakly alkaline?
In increasing order of hydrogen ion concentration, pH 11(C) < pH 9(E) < pH 7 (D) < pH 4 (A) < pH 1 (B) PH11 – Strongly alkaline pH9 – Weakly alkaline PH7 – Neutral pH4 – Weakly acidic pH1 – Strongly acidic
- ScienceClass 10CBSE
Why do acids not show acidic behaviour in the absence of water?
The acidic behaviour of acids is because of the presence of hydrogen ions. Hydrogen ions can only be produced in the presence of water, and therefore, water is definitely needed if acids are to show their acidic behaviour.
- ScienceClass 10CBSE
Why does distilled water not conduct electricity, whereas rain water does?
Distilled water does not contain any ionic compounds in it. Whereas rainwater has a lot more compounds. Rainwater has dissolved acidic gas, such as carbon dioxide from the air, and that forms carbonic acid. This means that it has hydrogen ions and carbonate ions. Therefore, with the presence of acids, rainwater can conduct electricity.
- ScienceClass 10CBSE
Compounds such as alcohols and glucose also contain hydrogen but are not categorised as acids. Describe an activity to prove it.
Insert two nails into the wooden or rubber cork and place them on a beaker, as shown in the figure. Connect the iron nail to a bulb, a 6-volt battery and a wire connected to the switch. Pour some alcohol or glucose so as to dip the nails in glucose or alcohol. Turn the switch on, and you see the bulb not glowing despite of connection to the switch. Now empty the beaker and add the HCL solution. This time, the bulb glows. This proves acid can conduct electricity, but alcohol and
- ScienceClass 10CBSE
Write word equations and then balanced equations for the reaction taking place when (a) Dilute sulphuric acid reacts with zinc granules. (b) Dilute hydrochloric acid reacts with magnesium ribbon. (c) Dilute sulphuric acid reacts with aluminium powder. (d) Dilute hydrochloric acid reacts with iron filings.
(a) Dilute sulphuric acid reacts with zinc granules. => Dilute sulphuric acid + zinc → Zinc Sulphate + Hydrogen Gas => H2SO4(aq) + Zn → ZnSO4(aq) + H2(g) (b) Dilute hydrochloric acid reacts with magnesium ribbon. => Dilute Hydrochloric + Magnesium → Magnesium Chloride + Hydrogen Gas <stro
- ScienceClass 10CBSE
Which one of the following types of medicines is used for treating indigestion? (a) Antibiotic (b) Analgesic (c) Antacid (d) Antiseptic
Indigestion is due to the excess production of acid in the stomach. Medicines used to treat indigestion is called Antacid.
- ScienceClass 10CBSE
10 mL of a solution of NaOH is found to be completely neutralised by 8 mL of a given solution of HCl. If we take 20 mL of the same solution of NaOH, the amount of HCl solution (the same solution as before) required to neutralise it will be (a) 4 mL (b) 8 mL (c) 12 mL (d) 16 mL
Solution: Since 10 ml of NaOH requires 8 mL of HCL, 20 ml of NaOH requires 8 x 2 = 16mL of HCl. Hence, the answer is option (d) 16mL.
- ScienceClass 10CBSE
A solution reacts with crushed eggshells to give a gas that turns lime-water milky. The solution contains a) NaCl (b) HCl (c) LiCl (d) KCl
The answer is HCl. Eggshells contain calcium carbonate, which on reaction with HCl, liberates CO2 gas, which turns lime water into milky. CaCO3 + 2HCl → CaCl2 + H2O + CO2
- ScienceClass 10CBSE
A solution turns red litmus blue, its pH is likely to be a) 1 (b) 4 (c) 5 (d) 10
Solution: The answer is 10 because litmus paper turns blue when the solution reacts with a basic solution (PH more than 7). Hence, 10 is the answer.
- ScienceClass 10CBSE
Write an equation to show the reaction between Plaster of Paris and water.
The chemical equation for the reaction of Plaster of Paris and water is CaSO4.1/2H2O + 3/2H2O → CaSO4.2H2O
- ScienceClass 10CBSE
What will happen if a solution of sodium hydrocarbonate is heated? Give the equation of the reaction involved.
Heating sodium hydrocarbonate yields sodium carbonate, and carbon dioxide gas is liberated in the process.