Solution of Chapter 9. Hydrogen (Chemistry - Exemplar Book)

Hydrogen resembles halogens in many respects for which several factors are responsible. Of the following factors which one is most important in this respect?

Why does H+ ion always get associated with other atoms or molecules?

Metal hydrides are ionic, covalent or molecular in nature. Among LiH, NaH, KH, RbH, CsH, the correct order of increasing ionic character is

Which of the following hydrides is electron-precise hydride?

Radioactive elements emit α, β and γ rays and are characterised by their halflives. The radioactive isotope of hydrogen is

Consider the reactions

(A) H₂O₂ + 2HI → I₂ + 2H₂O

(B) HOCl + H₂O₂→ H₃ O⁺ + Cl^- + O₂

Which of the following statements is correct about H₂O₂ with reference to these reactions? Hydrogen perioxide is _______

The oxide that gives H₂O₂ on treatment with dilute H₂SO₄ is —

Which of the following equations depict the oxidising nature of H₂ O₂?

Which of the following equation depicts reducing nature of H₂O₂?

Hydrogen peroxide is _________.

Which of the following reactions increases production of dihydrogen from synthesis gas?

When sodium peroxide is treated with dilute sulphuric acid, we get ______.

Hydrogen peroxide is obtained by the electrolysis of ______.

Which of the following reactions is an example of use of water gas in the synthesis of other compounds?

Which of the following ions will cause hardness in water sample?

Which of the following compounds is used for water softening?

Elements of which of the following group(s) of periodic table do not form hydrides.

Only one element of ________ forms hydride.

Which of the following statements are not true for hydrogen?

Dihydrogen can be prepared on commercial scale by different methods. In its preparation by the action of steam on hydrocarbons, a mixture of CO and H₂ gas is formed. It is known as ____________.

Which of the following statement(s) is/are correct in the case of heavy water?

Which of the following statements about hydrogen are correct?

Some of the properties of water are described below. Which of them is/are not correct?

Hardness of water may be temporary or permanent. Permanent hardness is due to the presence of

Which of the following statements is correct?

Which of the following statements is correct?

Which of the following statements is correct?

How can production of hydrogen from water gas be increased by using water gas shift reaction?

What are metallic/interstitial hydrides? How do they differ from molecular hydrides?

Name the classes of hydrides to which H₂O, B₂ H₆ and NaH belong.

If same mass of liquid water and a piece of ice is taken, then why is the density of ice less than that of liquid water?

Complete the following equations:

(i) PbS (s) + H₂O₂ (aq) →

(ii) CO (g) + 2H₂ (g) →

Give reasons:

(i) Lakes freeze from top towards bottom.

(ii) Ice floats on water.

What do you understand by the term ‘auto protolysis of water’ ? What is its significance?

Discuss briefly de-mineralisation of water by ion exchange resin.

Molecular hydrides are classified as electron deficient, electron precise and electron rich compounds. Explain each type with two examples.

Explain each type with two examples.

How is heavy water prepared? Compare its physical properties with those of ordinary water.

Write one chemical reaction for the preparation of D₂O₂

Calculate the strength of 5 volume H₂O₂ solution.

(i) Draw the gas phase and solid phase structure of H₂O₂.

(ii) H₂O₂ is a better oxidising agent than water. Explain.

Melting point, enthalpy of vapourisation and viscosity data of H₂O and D₂O is given below :

On the basis of this data explain in which of these liquids intermolecular forces are stronger?

Dihydrogen reacts with dioxygen (O2) to form water. Write the name and formula of the product when the isotope of hydrogen which has one proton and one neutron in its nucleus is treated with oxygen. Will the reactivity of both the isotopes be the same towards oxygen? Justify your answer.

Explain why HCl is a gas and HF is a liquid.

When the first element of the periodic table is treated with dioxygen, it gives a compound whose solid state floats on its liquid state. This compound has an ability to act as an acid as well as a base. What products will be formed when this compound undergoes autoionisation?

Rohan heard that instructions were given to the laboratory attendent to store a particular chemical i.e., keep it in the dark room, add some urea in it, and keep it away from dust. This chemical acts as an oxidising as well as a reducing agent in both acidic and alkaline media. This chemical is important for use in the pollution control treatment of domestic and industrial effluents.

(i) Write the name of this compound.

(ii) Explain why such precautions are taken for storing this chemical.

Give reasons why hydrogen resembles alkali metals?

Hydrogen generally forms covalent compounds. Give reason.

Why is the Ionisation enthalpy of hydrogen higher than that of sodium?

Basic principle of hydrogen economy is transportation and storage of energy in the form of liquid or gaseous hydrogen. Which property of hydrogen may be useful for this purpose? Support your answer with the chemical equation if required.

What is the importance of heavy water?

Write the Lewis structure of hydrogen peroxide.

An acidic solution of hydrogen peroxide behaves as an oxidising as well as reducing agent. Illustrate it with the help of a chemical equation.

With the help of suitable examples, explain the property of H2O2 that is responsible for its bleaching action?

Why is water molecule polar?

Why does water show high boiling point as compared to hydrogen sulphide? Give reasons for your answer.

Why can dilute solutions of hydrogen peroxide not be concentrated by heating. How can a concentrated solution of hydrogen peroxide be obtained?

Why is hydrogen peroxide stored in wax lined bottles?

Why does hard water not form lather with soap?

Phosphoric acid is preferred over sulphuric acid in preparing hydrogen peroxide from peroxides. Why?

How will you account for 104.5° bond angle in water?

Write redox reaction between fluorine and water.

Write two reactions to explain amphoteric nature of water.

Correlate the items listed in Column I with those listed in Column II. Find out as many correlations as you can.

Match Column I with Column II for the given properties/applications mentioned therein.

Match the terms in Column I with the relevant item in Column II.

Match the items in Column I with the relevant item in Column II.

In the following questions a statement of Assertion (A) followed by a statement of Reason (R) is given. Choose the correct option out of the options given below each question.

Assertion (A) : Permanent hardness of water is removed by treatment with washing soda.

Reason (R) : Washing soda reacts with soluble magnesium and calcium sulphate to form insoluble carbonates.

(i) Statements A and R both are correct and R is the correct explanation of A.

(ii) A is correct but R is not correct.

(iii) A and R both are correct but R is not the correct explanation of A.

(iv) A and R both are false.

In the following questions a statement of Assertion (A) followed by a statement of Reason (R) is given. Choose the correct option out of the options given below each question.

Assertion (A) : Some metals like platinum and palladium, can be used as storage media for hydrogen.

Reason (R) : Platinum and palladium can absorb large volumes of hydrogen.

(i) Statements A and R both are correct and R is the correct explanation of A.

(ii) A is correct but R is not correct.

(iii) A and R both are correct but R is not the correct explanation of A.

(iv) A and R both are false.

Atomic hydrogen combines with almost all elements but molecular hydrogen does not. Explain

How can D₂O be prepared from water? Mention the physical properties in which D₂O differs from H₂O. Give at least three reactions of D₂O showing the exchange of hydrogen with deuterium.

How will you concentrate H₂O₂? Show differences between structures of H₂O₂ and H₂O by drawing their spatial structures. Also mention three important uses of H₂O₂.

(i) Give a method for the manufacture of hydrogen peroxide and explain the reactions involved therein.

(ii) Illustrate oxidising, reducing and acidic properties of hydrogen peroxide with equations.

What mass of hydrogen peroxide will be present in 2 litres of a 5 molar solution? Calculate the mass of oxygen which will be liberated by the decomposition of 200 mL of this solution.

A colourless liquid ‘A’ contains H and O elements only. It decomposes slowly on exposure to light. It is stabilised by mixing urea to store in the presence of light.

(i) Suggest possible structure of A.

(ii) Write chemical equations for its decomposition reaction in light.

An ionic hydride of an alkali metal has significant covalent character and is almost unreactive towards oxygen and chlorine. This is used in the synthesis of other useful hydrides. Write the formula of this hydride. Write its reaction with Al₂Cl₆.

Sodium forms a crystalline ionic solid with dihydrogen. The solid is non-volatile and non- conducting in nature. It reacts violently with water to produce dihydrogen gas. Write the formula of this compound and its reaction with water. What will happen on electrolysis of the melt of this solid?