Chhattisgarh State Class 10 Science Chapter 2 Acids, Bases and Salts Solution
Acids, Bases and Salts
1) Choose the correct option
(i) In lemon juice: – (a) H+ ions are more, OH– ions are less
(b) H+ ions are less, OH– ions are more
(c) H+ ions and OH– ions are equal
(d) Only H+ ions are present.
Ans: – Option (a).
(ii) When an acid reacts with a metal carbonate then we get-
(a) Salt and water
(b) Salt and water and carbon dioxide
(c) Salt and sulphur dioxide
(d) Salt and hydrochloric acid are.
Ans: – Option (b).
(iii) Which among the following is not a strong acid
(a)HCl (b) HNO3
(c) CH3COOH (d) H2SO4.
Ans: – Option (c).
(iv) The pH of a neutral solution is
(a) 1 (b) 0
(c) 14 (d) 7.
Ans: – option (d) 7.
(v) Sakina has a burning sensation in her stomach due to acidity; she needs. : –
(a) A strong acid (b) A strong base
(c) A weak base (d) A weak acid.
Ans: – option ( b) A strong base.
(vi) The cause of tooth decay is pH of saliva
(a) Being less than 6.5 (b) Becoming 7
(c) Being less than 5.5 (d) Being more than 6.5.
Ans: – option (c).
(vii) Which of the following salts is acidic in nature
(a) NaCl (b) Na2SO4
(c) NH4Cl (d) KNO3.
Ans: – Option (c).
2) Write the names of any two acids found in the food that we eat.
Ans: – The acid which present in the food that we eat is citric acid of lemon and lactic acid in milky product.
3) How do we distinguish between acids and bases using an olfactory indicator?
Ans: – In an olfactory indicator there used vanilla or onion extract which after the reaction with acid the sound is vanished but with the reaction with bases there are no changes in the smell which clearly distinguished between the acid and base.
4) The pH of fresh milk is 6. What will be the pH when it sets into curd/yogurt?
Ans: – The PH of the milk decrease while it sets into curd. The PH is decrease as lactic acid are formed from milk. And the PH range of this lactic acid or yogurt is 7 4.5 to 5.5.
5) You have been given three test tubes. One of them has distilled water and of the remaining two, one has an acid and the second has a basic solution. If you only have red litmus paper then how will how identify the nature of solutions in each of the test tubes?
Ans: – In the first test tube as there are distilled water then the colour of the red litmus will change. And in the second test tube there are acid solution so there will be no change in colour while putting the red litmus. In the remaining test tube, there are base solution so the red litmus will change into blue.
6) During an experiment, Neelam and Manish added concentrated sulphuric acid to dry (anhy-drous) sodium chloride. A gas evolved during the reaction. When Manish placed a dry bluelitmus paper near the mouth of the test tube nothing happened but when he placed a moistblue litmus paper, it became red. Explain why.
Ans: – When Neelam and Manish added concentrated H2SO4 to dry NaCl then hydrogen chloride gas is produces.
H2SO4 + NaCl –> HCl + Na2SO4 ;
This hydrogen chloride gas when came in contact to wet litmus it becomes red but when it came in contact with dry litmus it doesn’t show any changes.
7) Some substances and their pH values are givenin the table. Analyse the data in the table and answer the following questions:
| Substance | PH value |
| Solution of baking soda | 8.2 |
| Lemon juice | 2.2 |
| vinegar | 5.5 |
| Sodium hydroxide | 13 |
| water | 7 |
(a) Which of the substances are basic in nature?
(b) Which of the substances are acidic in nature?
(c) Which of the substances are neutral?
Ans: – (a) From the upper table we can say baking soda and sodium hydroxide has the PH value above 7 so these are basic in nature.
(b) In the table lemon juice and vinegar are acidic in nature as their PH value is under 7.
(c) As water has PH value of 7 it is neutral in nature.
8)Acid’s “A” and “B” were taken in two beakers. Acid “A” ionizes partially in water while acid “B” ionizes completely. On this basis, tell:
(a) Which among “A” and “B” is strong acid and which is weak?
(b) What is a weak acid?
(c) What is a strong acid?
(d) Give examples of both strong and weak acids.
Ans: – (a ) As the acid a is ionized partially in water it is weak acid. And the acid B is ionized completely it is strong acid.
(b) A weak acid doesn’t dissolve or ionized property in water. In the upper experiment the A is weak acid as it doesn’t ionize completely.Example: – Acetic acid.
(c) If any acid completely ionized in a water solution, then that acid will be called a strong acid. Example: – Nitric acid.
(d) A strong acid is HCl or hydrochloric acid, nitric acid (HNO3) and a weak acid is CH3COOH or acetic acid.
9) Which gas is usually displaced during reaction between acids and a metal? How will you test this gas? Take the example of magnesium metal to explain.
Ans: – In a reaction between metal and acids salt and hydrogen gas is produced.
Metal + acid –> salts + hydrogen;
By splint test we can assure that it is a hydrogen gas.
Example: – Mg + 2HCl –> MgCl2 + H2;
10) When an egg shell is reacted with dilute hydrochloric acid, foaming is observed and an effer-vescent gas is produced. Once foaming subsides, a lighted agarbatti is extinguished on placing it inside test tube. Explain the following in the given activity:
(a) Procedure or steps followed in the activity
(b) Draw the picture of the experimental set-up
(c) Write the balanced chemical equation of the reaction taking place.
Ans: – The steps which are take while doing this experiment are –
- 5ml of 20% HCl solution are taken in a test tube.
- Egg shell of some amount are poured in the test tube.
- Now when we place any agarbatti in mouth of the test tube we seen that agarbatti flame is extinguished.
(b)
(c) The balanced chemical reaction is: –
CaCO3 + 2HCl —> CaCl2 +CO2 + H2O;
11) The pH of soil in Tikeshweri’s field is 4.2. How can she control the pH of her soil so that shegets a good paddy crop?
Ans: – The soil is seen clearly acidic in nature so for the control of the PH of the soil she must add some basic substance. So basic substance like calcium hydroxide (Ca (OH)2) can be added.
12) What is neutralization reaction? Explain and give two examples.
Ans: – When after reaction between acid and base makes the product water and salt then this reaction can call neutralization reaction.
Example: – HCl (acid) + NaOH (base) —>NaCl (salt) + H2O;
13) Samaru added baking soda to raw milk so that its pH changed from 6 to 8. This milk will takelonger to change into curd; why?
Ans: – After adding the baking soda to the milk the solution become basic. As the baking soda made the solution to the PH of 8 which is basic in nature this milk takes some times to form curd. For this phenomenon to forming curd time is needed.
14) What is a salt? How is the nature of a salt determined? Take NH4NO3 and Na2CO3 asexamples and explain.
Ans: – The reaction between the acid and base produce salts and water.
If any reaction acid is strong then the salt is acidic in nature and if the base is strong then the salt is basic in nature.
The NH4NO3 is salt which is acidic in nature as at the time of producing this salt acid solution was more powerful whereas for producing the basic salts like Na2CO3 the solution was more basic in nature.