Class 10 Science Acid base and Salts Extra Questions
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a. One Marks Questions
b. Two Marks Questions
c. Long answer questions(5 Marks)
One Mark Questions
Question (1)
Why does the flow of acid rain water into a river make the survival of aquatic life in the river difficult? Question (2)
Write balanced chemical equations for the reactions taking place when dry blue crystals of copper sulphate are dropped into concentrated sulphuric acid. Question (3)
Name the products formed when sodium hydrogen carbonate is heated. Write the chemical equation for the reaction involved.
Answer
Formula of sodium hydrogen carbonate is NaHCO3.
when it is heated it forms water , carbon dioxide and and sodium carbonate.
2NaHCO3 --> H2O + CO2 + Na2CO3
Question (4)
Two solutions A and B have pH values of 5 and 8 respectively. Which solution will be basic in nature?
Answer
Solution B as pH > 7
Question (5)
Why does tooth decay start when the pH of mouth is lower than 5.5? Question (6) How is the concentration of hydronium ions (H3O+) affected when a solution of an acid is diluted? Question (7) Fresh milk has a pH of 6. When it changes into curd (Yogurt), will its pH value increase or decrease? Why?
Answer
Fresh milk has a pH of 6, before conversion. When milk is turned into curd then its pH value will decrease due to the production of lactic acid in curd which is acidic in nature.
Question (8)
A dry pellet of a common base B, when kept in open absorbs moisture and turns sticky. The compound is also a by – product of chlorine – alkali process. Identify B. What type of reaction occurs when B is treated with an acidic oxide? Write a balanced chemical equation for one such solution. Question (9)
Name the acid present in an ant sting.
Two Marks Questions
Question (1)
Write the chemical formula for bleaching powder. How is bleaching powder prepared? For what purpose is it used in paper factories? Question (2)
(i) An aqueous solution has a pH of 7.0. Is this solution acidic, basic or neutral?
(ii) Which has higher pH value, 1 M HCI or 1 M NaOH?
Answer
(i) Neutral
(ii) NaOH has more pH value
Question (3)
Name the gas which is usually produced when dilute sulphuric acid reacts with a metal. Illustrate it with an example. How will you test the evolution of this gas? Question (4)
A metal compound ‘A’ reacts with dilute sulphuric acid to produce a gas which extinguishes a burning candle. Identify the compound ‘A’ and the a gas produced. Write a balanced chemical equation for the reaction if one of the compounds formed in the reaction is sodium sulphate. Question (5)
State what happens when zinc granules are heated with sodium hydroxide solution. Write the balanced equation for this reaction. Name the main product formed in this reaction. Question (6)
Give reasons for the following:
(a) Dry HCI does not change the colour of dry litmus paper.
(b) Aqueous solution of an acid conducts electricity.
Answer
The colour of litmus paper changes only in the presence of ions like hydrogen (H+) or hydronium (H3O+) ions. HCl can produce these ions only in the form of aqueous solution. Hence dry HCl gas does not change the colour of dry litmus paper
Question (7)
While diluting an acid, why is it recommended that acid should be added to water and not water to the acid? Question (8)
P and Q are aqueous solution of sodium chloride and sodium hydroxide respectively. Which of these will turn:
(a) Blue litmus to red or
(b) Red litmus to blue? Give justification for your answer.
Answer
Solution P no effect on litmus paper since it is neutral
Solution Q it is strong base so it turns red to blue litmus
Question (9)
What is universal indicator? State the purpose for which this indicator is used. Question (10)
Name the acid produced in our stomach. What happens if there is an excess of acid in the stomach? How can it be cured? Name one antacid?
Answer
our stomach produces hydrochloric acid. It helps in the digestion of food without harming the stomach.During indigestion the stomach produces too much acid and this causespain and irritation. To get rid of this pain, people use bases called antacids. These antacids neutralise the excess acid.Magnesium hydroxide (Milk of magnesia), a mild base, is often used for this purpose
Question (11)
Define an acid and a base. Name one weak acid and one strong base. Question (12)
Explain why an aqueous solution of sodium sulphate is neutral while an aqueous solution of sodium carbonate is basic in nature?
Answer
Because Sodium sulphate salt is made by reaction of sulphuric acid (strong acid) the sodium hydroxide (strong base) , thus on combining the opposite effects of acid and base neutralize each others effect completely leading to the formation of a neutral salt.
Sodium carbonate salt is made of reaction of carbonic acid and sodium hydroxide . on combining the basic character will be more as a week acid can not neutralize a strong base completely . so the salt formed is basic in nature
Question (13)
How does the enamel of the teeth undergo damage due to the eating of chocolates? What should be done to prevent it? Question (14)
(a) Three acidic solutions A, B and C have pH = 0, 3 and 5 respectively.
(i) Which solution has the highest concentration of H+ ions?
(ii) Which solution has the lowest concentration of H+ ions?
(b) How concentrated sulphuric acid can be diluted? Describe the process.
Answer
Solution A has highest concentration of H+ ions and Solution C has the lowest concentration of H+ ions
concentrated sulphuric acid can be diluted using water. We need to add small amount of acid in the water not the water to the acid.
Question (15)
Fresh milk has a pH of 6. How do you think the pH will change to curd? Explain. Question (16)
State in brief the method of preparation of bleaching powder. Give a balanced chemical equation of the reaction involved. Question (17) Give two uses of baking soda and washing soda each. Question (18)
When zinc metal is treated with a dilute solution of a strong acid, a gas is evolved, which is utilized in the hydrogenation of oil. Name the gas evolved. Write the chemical equation of the reaction and also write a test to detect the gas formed. Question (19)
State for what purpose is bleaching powder used in water treatment plants. Question (20)
How would you distinguish between baking powder and washing soda by heating? Question (21)
Salt A commonly used in bakery products on heating gets converted into another salt B which itself is used for removal of hardness of water and a gas C is evolved. The gas C when passed through lime water turns it milky. Identify A, B and C. Question (22)
What are strong and weak acids? In the following list of acids, separate strong acids from weak acids: Hydrochloric acid, citric acid, acetic acid, nitric acid, formic acid, sulphuric acid.
Question (1)
On passing excess CO2 through lime water, it first turns milky and then becomes colourless. Explain why? Write the chemical reactions.
Answer
The first reaction produces CaCO3 which is insoluble in water and hence the solution turns milky.
Ca(OH)2 [lime water] + CO2 -- CaCO3 + H2O
If furthermore CO2 is passed,the CaCO3 reacts with the CO2 to form Ca(HCO3)2 which is soluble in water and hence the solution becomes colourless.
CaCO3 + CO2 + H2O -- Ca(HCO3)2
Question (2)
While eating food, you happen to spill some curry on your white shirt. You immediately scrub it with soap. What happens to its yellow colour on scrubbing with soap? Why? What happens to this stain when the shirt is washed with plenty of water? Question (3)
Explain the action of dilute hydrochloric acid on the following with chemical equations:
(a) Magnesium ribbon
(b) Sodium hydroxide
(c) Crushed egg shells
Answer
The formula equation for this experiment is:
Mg + 2HCl ->MgCl2 + H2
HCL + NaOH -> Nacl + H2O
Egg shells contains calcium carbonate, which on reaction with HCl liberates CO2 gas
CaCO3 + 2HCl ? CaCl2 + H2O + CO2
Question (4)
What are products formed when an acid reacts with a base? What is the type of reaction? Give one example and name the salt obtained. Question (5)
On adding dilute hydrochloric acid to copper oxide powder, the solution formed is blue - green.
(a) Identify the compound formed which gives blue -green colour to the solution.
(b) Write its balanced chemical equation.
(c) On the basis of above reaction, what should be the nature of copper oxide?
Answer
When HCl reacts with copper oxide, a blue green solution of copper (II) chloride is formed. The reaction is as follows:
HCl + CuO --------> CuCl2 + H2O
(aq) (s) (aq) (l)
Question (6)
Sugandha prepares HCI gas in her school laboratory using certain chemicals. She puts both dry and wet blue litmus papers in contact with the gas.
(i) Name the reagents used by Sugandha to prepare HCI gas.
(ii) State the colour changes observed with the dry and wet blue litmus paper.
(iii) Show the formation of ions when HCI gas combines with water. Question (7)
How the following substances will dissociate to produce ions in their solution?
(a) Hydrochloric acid
(b) Nitric acid
(c) Sulphuric acid
(d) Sodium hydroxide
(e) Potassium hydroxide
(f) Magnesium hydroxide
Answer
Question (8)
Differentiate between strong electrolytes and weak electrolytes. Mention two examples of each. Question (9)
State reasons for the following:
(a) A tarnished copper vessel begins to shine again rubbed with lemon.
(b)All alkalis are bases but all bases are not alkalis.
(c) Use of a mild base like baking soda on the honey – bee stung area gives relief. Question (10)
(a) State what happens when an acid reacts with a base? Name the reaction and give equation of the reaction involved.
(b) Name one natural source of each of the following acids:
(i) Citric acid
(ii) Oxalic acid
(iii) Lactic acid
(iv) Tartaric acid
(v) Acetic acid
Answer
citric acid in lemon
oxalic acid in tomato
lactic acid in curd
tartaric acid in tamarind
Acetic acid in vinegar
Question (11)
A student mixed equal volumes of hydrochloride acid and sodium hydroxide solutions of same concentration.
(i) What would be the pH and colour of pH paper of the resulting solution and why?
(ii) Write the chemical equation of the reaction involved. Question (12) State the colour change on treating pH paper with the folloing solutions:
sodium hydroxide solution, water, sulphuric acid solution, calcium hydroxide solution. Arrange the following solutions in increasing order of pH. Question (13)
(a) Name the acid produced in our stomach. What happens when there is an excess secretion of acid in the stomach? How can its effect be cured?
(b) Explain how pH change is the cause of tooth decay? How it can be prevented?
(c) What is the ideal soil pH for the growth of plants? Explain with the help of an activity how will you test the pH of a sample of soil collected from your locality? Question (14)
Name one indicator which specifies the various levels of H+ ion concentration.
Summary
This Class 10 Science Acid base and Salts Extra Questions with answers is prepared keeping in mind the latest syllabus of CBSE . This has been designed in a way to improve the academic performance of the students. If you find mistakes , please do provide the feedback on the mail.
