CBSE Class 10 Science — Acids, Bases and Salts

Which one of the following can be used as an acid-base indicator by a visually impaired (blind) student?

In the following diagram, if acetic acid of same concentration is taken in place of dilute sulphuric acid, then

Study the following table and select the correct option: Salt | Acid used | Base used | Nature of Salt (A) NaCl | HCl | NaOH | Basic (B) $Na_2CO_3$ | $H_2CO_3$ | NaOH | Neutral (C) $Na_2SO_4$ | $H_2SO_4$ | NaOH | Acidic (D) $CH_3COONa$ | $CH_3COOH$ | NaOH | Basic

Four solutions, namely fructose, ethanol, hydrochloric acid and sodium hydroxide filled in four separate beakers are connected one by one in an electric circuit with a bulb. The solutions in which the bulb will glow when current is passed are:

The natural sources of oxalic acid, lactic acid and methanoic acid respectively are:

How is a universal indicator obtained? How is the wide range of pH of solution tested by it?

Write the preparation of Baking soda. How does it help in making cakes soft and spongy?

(a) Explain chlor-alkali process with chemical equation. Name the products formed at anode and cathode. OR (b) Write the preparation of following compounds with balanced chemical equation: (i) Baking soda (ii) Bleaching powder (iii) Plaster of Paris

(A) (a) Give the chemical name and formula of Plaster of Paris. (b) Write the chemical equation of its preparation. (c) Give any two uses of it. OR (B) (a) Name the acid present in ant's sting. (b) Give reason: (i) While diluting an acid, it is recommended that the acid should be added to water. (ii) Baking soda is used as an antacid.

In order to prepare dry hydrogen chloride gas in humid atmosphere the gas produced is passed through a guard tube (drying tube) which contains :

The warning sign shown in the given figure must invariably be displayed/pasted on the containers which contain hydroxide of:

Which of the given option represents a family of salts ?

You have three aqueous solutions A, B and C as given below: A - Potassium nitrate, B - Ammonium chloride, C - Sodium carbonate. The ascending order of the pH of these solutions is:

The body of human beings works within the pH range of:

A common feature observed in the crystals of washing soda, copper sulphate, gypsum and ferrous sulphate is that all

Consider the following reactions : (i) Dilute hydrochloric acid reacts with sodium hydroxide. (ii) Magnesium oxide reacts with dilute hydrochloric acid. (iii) Carbon dioxide reacts with sodium hydroxide. It is found that in each case :

Juice of tamarind turns blue litmus to red. It is because of the presence of a chemical compound called:

The water of crystallization is present in: (i) Bleaching Powder (ii) Plaster of Paris (iii) Washing Soda (iv) Baking Soda

Assertion (A): Concentrated nitric acid is diluted by adding water slowly to acid with constant stirring. Reason (R): Concentrated nitric acid is easily soluble in water.

A crystalline substance of green colour 'X' emits gases of characteristic odour when heated over a flame. It first loses water and changes colour. On further heating, it decomposes and produces a solid compound Y. (a) Identify 'X' and 'Y'. (b) State the change in colour observed when 'X' is heated.

(a) Write the formula of the ions which (i) acids, and (ii) bases generate in water solutions. (b) Dry HCl gas does not change the colour of dry litmus paper. Why?

Write chemical formula of washing soda. How is it obtained from baking soda? List two uses of washing soda.

(a) State the chemical property in each case on which the following uses of baking soda are based upon: (i) as an anti-acids (ii) as a constituent in making baking powder (iii) in soda-acid fire-extinguishers OR (b) Write chemical equations to show what happens when an acid reacts with a (i) metal (ii) base and (iii) carbonate. Write the name of the main product formed in each case.

(a) Common salt is an important raw material for various chemicals of daily use. State in brief the method of preparation of (i) Sodium hydroxide, and (ii) Sodium hydrogen carbonate from common salt. Write balanced chemical equations of the reactions that occur. OR (b) Design an experimental set-up to demonstrate that "Alcohol and glucose contain hydrogen but are not categorised as acids". Also give the reason to justify this fact.

'A' and 'B' are two salts used for washing purposes. Salt 'A' is used for bathing also. Four test tubes I, II, III and IV as mentioned below are taken. I. Rain water + solution of salt 'A' II. Rain water + solution of salt 'B' III. Tubewell water + solution of salt 'A' IV. Tubewell water + solution of salt 'B' The test tubes are shaken one by one almost identically for the same time and the lengths of foam formed in each test tube is noted. (a) In which one of the four test tubes is the foam formed the minimum ? [1] (b) Differentiate between salt A and salt B. [1] (c) (i) What are esters ? What happens when an ester reacts with an alkali (say sodium hydroxide) ? Give chemical equation for the reaction. [2] OR (c) (ii) What is the cause of hardness of water ? Sometimes it is observed that while bathing foam is formed with difficulty and an insoluble substance is formed. Name this substance and write the cause of its formation. [2]

Acid-base indicators can be used to distinguish between an acid and a base. Universal indicator, a mixture of several indicators, shows different colours at different concentrations of acids and bases, thereby indicating their pH on the pH scale of $0-14$. The pH of a solution is measured by pH paper, which is a paper impregnated with a universal indicator. Answer the following questions: (a) Solution P is a strong acid while solution Q is a strong base. On the pH scale, where would you place the solutions P and Q? [1] (b) A solution has a pH of 7. Name a compound you would use to (i) increase its pH, and (ii) decrease its pH. [1] (c) (i) When the pH of a solution is decreased from 4 to 2, what effect does it produce on its hydronium ion concentration? State the colour change shown by the pH paper. [2] OR (c) (ii) A person is feeling pain and irritation in the stomach due to indigestion. What could be the pH of the fluid in the stomach? Write the common name of the medicines people use for remedy. Give the chemical name of "milk of magnesia" often used for this purpose. [2]

Seawater contains many salts dissolved in it. Common salt is separated from these salts. Deposits of solid salt are also found in several parts of the world. These large crystals are often brown due to impurities. This is called rock salt and is mined like coal. The common salt is an important raw material for chemicals of daily use. (a) Write balanced chemical equations to show the products formed during electrolysis of brine. [1] (b) List two uses of any one product obtained during electrolysis of brine. [1] (c) (i) A mild non-corrosive basic salt 'A', used for faster cooking, is strongly heated to produce a compound 'B', that is used for removing permanent hardness of water. Identify A and B and also write the equation for the reaction that occurs when A is heated. [2] OR (c) (ii) Define water of crystallisation. Give two examples of salts that have water of crystallisation. [2]

Juice of tamarind turns blue litmus to red. It is because of the presence of an acid called :

Select a pair of natural indicator from the following:

An aqueous solution of a salt turns blue litmus to red. The salt could be the one obtained by the reaction of :

Four solutions, namely glucose, alcohol, hydrochloric acid and sulphuric acid filled in four separate beakers are connected one by one in an electric circuit with a bulb. The solutions in which the bulb will glow when current is passed are:

The salt present in tooth enamel is :

A chemical compound used in glass, soap and paper industries is

An aqueous solution of sodium chloride is prepared in distilled water. The pH of this solution is :

(a) 1 gram of solid sodium chloride was taken in a clean and dry test tube and concentrated sulphuric acid was added to it. (i) Name the gas evolved in the reaction. (ii) What will be observed when this gas is tested with (I) dry, and (II) wet blue litmus paper? Write your conclusion about the nature (acidic/basic) of this gas. OR (b) Some metals react with acids to produce salt and hydrogen gas. Illustrate it with an example. How will you test the presence of this gas?

Write the common name and the chemical name of the compound $\mathrm{CaSO_4\cdot\frac{1}{2}H_2O}$. Write the method of its preparation. Give chemical equation for the reaction, when water reacts with $\mathrm{CaSO_4\cdot\frac{1}{2}H_2O}$.

(a) (i) Five solutions A, B, C, D and E when tested with pH paper showed pH as 4, 1, 13, 7 and 10 respectively. Which solution is: (1) Strongly acidic (2) Strongly alkaline (3) Weakly acidic (4) Neutral and (5) Weakly alkaline? Arrange the solutions in increasing order of $H^+$ ion concentration. (ii) Write the name and formula of (1) an acidic salt and (2) a basic salt giving the name of the parent acid and parent base used to form the salt in each case. OR (b) Name and state in brief the process which is used to prepare sodium hydroxide from sodium chloride. In this process along with the main product two gases 'X' and 'Y' are also given off at the two electrodes. Name 'X' and 'Y' specifying the name of their respective electrode at which each gas is obtained. One of these gases when reacts with dry calcium hydroxide produces a compound 'Z' which is widely used in water treatment plants and textile industries. Name Z and write chemical equation for the reaction involved in its formation.

(a) A few crystals of ferrous sulphate were taken in a dry boiling tube and heated. Tiny water droplets were observed in the tube after some time. (i) From where did these water droplets appear? Explain. (ii) What colour change will be observed during heating? (iii) How many molecules of water are attached per molecule of $\mathrm{FeSO_4}$ crystal? Write the molecular formula of crystalline forms of (I) Copper sulphate, and (II) Sodium carbonate. (iv) State how is Plaster of Paris obtained from gypsum. Write two uses of Plaster of Paris. OR (b) An acid 'X' present in tamarind when mixed with 'Y', produces a mixture 'Z'. 'Z' on addition to a dough when heated makes cakes soft and spongy. 'Y' is prepared from common salt and helps in faster cooking. (i) Write the common names of 'X', 'Y' and 'Z', and the chemical formula of 'Y'. (ii) How is 'Y' prepared and how does it help in making cakes soft and spongy? Illustrate the reaction with suitable chemical equation. (iii) Write the name and chemical formula of a mild base other than 'Y' used as an antacid.

Salts play a very important role in our daily life. Sodium chloride which is known as common salt is used almost in every kitchen. Baking soda is also a salt used in faster cooking as well as in baking industry. The family of salts is classified on the basis of cations and anions present in them. (a) Identify the acid and base from which Sodium chloride is formed. (1 mark) (b) Find the cation and the anion present in Calcium sulphate. (1 mark) (c) "Sodium chloride and washing soda both belong to the same family of salts." Justify this statement. (2 marks) OR (c) Define the term pH scale. Name the salt obtained by the reaction of Potassium hydroxide and Sulphuric acid and give the pH value of its aqueous solution. (2 marks)

When Sodium bicarbonate reacts with dilute hydrochloric acid, the gas evolved is :

In the experimental setup given below, it is observed that on passing the gas produced in the reaction in the solution 'X' the solution 'X' first turns milky and then colourless. The option that justifies the above stated observation is that 'X' is aqueous calcium hydroxide and

Select a pair of olfactory indicators from the following :

Few drops of aqueous solution of ammonium chloride are put on a universal indicator paper. The paper turns pink. Study the following table and choose the correct option. Table: | | Nature | Ammonium chloride is a salt of .... | Range of pH | |---|---|---|---| | (a) | acidic | weak acid and strong base | less than 7 | | (b) | basic | weak acid and strong base | more than 7 | | (c) | acidic | strong acid and weak base | less than 7 | | (d) | basic | strong acid and strong base | 7 |

When zinc reacts with sodium hydroxide, the product formed is :

The table below has information regarding $\mathrm{pH}$ and the nature (acidic/basic) of four different solutions. Which one of the options in the table is correct? | Option | Solution | Colour of pH paper | Approximate pH value | Nature of solution | |---|---|---|---|---| | (a) | Lemon juice | Orange | 3 | Basic | | (b) | Milk of magnesia | Blue | 10 | Basic | | (c) | Gastric juice | Red | 6 | Acidic | | (d) | Pure water | Yellow | 7 | Neutral |

Acid present in tomato is :

Fresh milk has a pH of 6. To delay its curdling, a chemical substance is added to it, which is :

Two salts 'X' and 'Y' are dissolved in water separately. When phenolphthalein is added to these two solutions, the solution 'X' turns pink and the solution 'Y' does not show any change in colour, therefore 'X' and 'Y' are Table: | | (X) | (Y) | |---|---|---| | (a) | $Na_2CO_3$ | $NH_4Cl$ | | (b) | $Na_2SO_4$ | $NaHCO_3$ | | (c) | $NH_4Cl$ | $Na_2SO_4$ | | (d) | $NaNO_3$ | $Na_2SO_4$ |

Sodium hydroxide is termed an alkali while Ferric hydroxide is not because :

The name of the salt used to remove permanent hardness of water is :

Select washing soda from the following:

Hydronium ions are formed by the reaction between :

Assertion (A) : It is advised that while diluting an acid one should add water to acid and not acid to water keeping the solution continuously stirred. Reason (R) : The process of dissolving an acid into water is highly exothermic.

Assertion (A): Sodium oxide is an amphoteric oxide. Reason (R): Metal oxides which react with both acids as well as bases are known as amphoteric oxides.

(a) (i) A compound 'X' which is prepared from gypsum has the property of hardening when mixed with proper quantity of water. Identify 'X' and write its chemical formula. (ii) State the difference in chemical composition between baking soda and baking powder. OR (b) Write balanced chemical equation for the reaction that occurs when: (i) blue coloured copper sulphate crystals are heated and (ii) Sodium hydrogen carbonate is heated during cooking.

(a) On heating $X'$ at $373\mathrm{K}$, it loses water molecules and becomes $Y'$. $Y'$ is a substance which doctors use for supporting fractured bones in the right position. (i) Identify $X'$ and $Y'$. (ii) How can $X'$ be reobtained from $Y'$? OR (b) Two solutions M and N give Red and Blue colour respectively with a universal indicator. (i) In which solution will the hydrogen ion concentration be more? Justify your answer. (ii) If both M and N solutions are mixed and the resultant mixture is tested with a universal indicator, it turns green. What is the nature of the salt formed? Justify your answer.

(A) A student took a small amount of copper oxide in a conical flask and added dilute hydrochloric acid to it with constant stirring. He observed a change in colour of the solution. (i) Write the name of the compound formed and its colour. (ii) Write a balanced chemical equation for the reaction involved. OR (B) The industrial process used for the manufacture of caustic soda involves electrolysis of an aqueous solution of compound 'X'. In this process, two gases 'Y' and 'Z' are liberated. 'Y' is liberated at cathode and 'Z', which is liberated at anode, on treatment with dry slaked lime forms a compound 'B'. Name X, Y, Z and B.

(a) Suggest one remedial measure each to counteract the change in pH in human beings in following cases: (i) Production of too much acid in stomach during indigestion (ii) Stung by a honey bee / nettle leaves (b) Fresh milk has a pH of 6. When it changes into curd will its pH increase or decrease? Why?

(i) Suggest a safe procedure of diluting a strong concentrated acid. (ii) Name the salt formed when sulphuric acid is added to sodium hydroxide and write its pH. (iii) Dry HCl gas does not change the colour of dry blue litmus paper. Why ?

(a) Sometimes the pH of our mouth gets lower than 5·5. Why? (b) A basic salt 'X' is obtained by heating baking soda followed by crystallisation. Identify 'X' and state its two industrial uses. (c) Why do copper sulphate crystals turn white on heating?

The teacher while conducting practicals in the laboratory divided the students into three groups and gave them various solutions to find out their pH and classify them into acidic, basic and neutral solutions. Group A - Lemon juice, vinegar, colourless aerated drink Group B - Tomato juice, coffee, ginger juice Group C - Sodium hydroxide, sodium chloride, lime water (a) For the solutions provided, which group is/are likely to have pH value (i) less than 7, and (ii) greater than 7 ? (b) List two ways of determining pH of a solution. (c) Explain, why the sour substances such as lemon juice are effective in cleaning the tarnished copper vessels. OR (c) "pH has great importance in our daily life." Justify this statement by giving two examples.

Baking soda is a mixture of:

The chemical formula for plaster of Paris is:

Several factories were pouring their wastes in rivers A and B. Water samples were collected from these two rivers. It was observed that sample collected from river A was acidic while that of river B was basic. The factories located near A and B are

A visually challenged student, has to perform a lab test to detect the presence of acid in a given solution. The acid-base indicator preferred by him will be:

An aqueous solution 'A' turns phenolphthalein solution pink. On addition of an aqueous solution 'B' to 'A', the pink colour disappears. The following statement is true for solution 'A' and 'B'.

If $10 \text{ mL}$ of $H_2SO_4$ is mixed with $10 \text{ mL}$ of $Mg(OH)_2$ of the same concentration, the resultant solution will give the following colour with universal indicator:

Complete and balance the following chemical equations : (i) $\text{NaOH}_{(aq)} + \text{Zn}_{(s)} \rightarrow$ (ii) $\text{CaCO}_{3(s)} + \text{H}_2\text{O}_{(l)} + \text{CO}_{2(g)} \rightarrow$ (iii) $\text{HCl}_{(aq)} + \text{H}_2\text{O}_{(l)} \rightarrow$ OR During electrolysis of brine, a gas 'G' is liberated at anode. When this gas 'G' is passed through slaked lime, a compound 'C' is formed, which is used for disinfecting drinking water. (i) Write formula of 'G' and 'C'. (ii) State the chemical equation involved. (iii) What is common name of compound 'C'? Give its chemical name.

OR How is washing soda prepared from sodium carbonate? Give its chemical equation. State the type of this salt. Name the type of hardness of water which can be removed by it?

List the important products of the Chlor-alkali process. Write one important use of each.

OR: (i) Draw a labelled diagram to show the preparation of hydrogen chloride gas in laboratory. (ii) Test the gas evolved first with dry and then with wet litmus paper. In which of the two cases, does the litmus paper show change in colour? (iii) State the reason of exhibiting acidic character by dry HCl gas / HCl solution.

Give reasons for the following: (i) Only one half of water molecule is shown in the formula of Plaster of Paris. (ii) Sodium hydrogen carbonate is used as an antacid. (iii) On strong heating, blue coloured copper sulphate crystals turn white.

A cloth strip dipped in onion juice is used for testing a liquid 'X'. The liquid 'X' changes its odour. Which type of an indicator is onion juice? The liquid 'X' turns blue litmus red. List the observations the liquid 'X' will show on reacting with the following: (a) Zinc granules (b) Solid sodium carbonate Write the chemical equations for the reactions involved. OR Define water of crystallisation. Give the chemical formula for two compounds as examples. How can it be proved that the water of crystallisation makes a difference in the state and colour of the compounds?

Blue litmus solutions is added to two test tubes A and B containing dilute HCl and NaOH solution respectively. In which test tube a colour change will be observed? State the colour change and give its reason.

What is observed when $2 mL$ of dilute hydrochloric acid is added to $1 g$ of sodium carbonate taken in a clean and dry test tube? Write chemical equation for the reaction involved.

2 mL of sodium hydroxide solution is added to a few pieces of granulated zinc metal taken in a test tube. When the contents are warmed, a gas evolves which is bubbled through a soap solution before testing. Write the equation of the chemical reaction involved and the test to detect the gas. Name the gas which will be evolved when the same metal reacts with dilute solution of a strong acid.

The pH of a salt used to make tasty and crispy pakoras is 14. Identify the salt and write a chemical equation for its formation. List its two uses.

When you add a few drops of acetic acid to a test-tube containing sodium bicarbonate powder, which one of the following is your observation?

Explain why, an aqueous solution of sodium sulphate is neutral while an aqueous solution of sodium carbonate is basic in nature.

State reason for the following: (i) Dry $\text{HCl}$ gas does not change the colour of the dry blue litmus paper. (ii) Alcohol and glucose also contain hydrogen, but do not conduct electricity. (iii) Concentration of $\text{H}_3\text{O}^+$ ion is affected when a solution of an acid is diluted.

Write balanced chemical equations for the following statements: (i) $\text{NaOH}$ solution is heated with zinc granules. (ii) Excess of carbon dioxide gas is passed through lime water. (iii) Dilute sulphuric acid reacts with sodium carbonate. (iv) Egg shells are dropped in hydrochloric acid. (v) Copper (II) oxide reacts with dilute hydrochloric acid.

Four students studied reactions of zinc and sodium carbonate with dilute hydrochloric acid and dilute sodium hydroxide solutions and presented their results as follows. The (✓) shows evolution of gas and (-) shows no reaction. The right set is:

Dilute $\text{NaOH}$ solution and solid sodium carbonate:

A student prepared 20% sodium hydroxide solution in a beaker containing water. The observations noted by him are given below. I. Sodium hydroxide is in the form of pellets. II. It dissolves in water readily. III. The beaker appears cold when touched from outside. IV. The red litmus paper turns blue when dipped into the solution. The correct observation are: