Selina solutions concise chemistry class 9 icse Solutions for Chapter 6 chapter 6 study of the first element hydrogen

Justify the position of Hydrogen in the periodic table.

Compare hydrogen with alkali metals on the basis of :

i) ion formation (ii) Reducing- power

iii) Reaction with oxygen (iv) Oxide formation

In what respect doses hydrogen differ from

i) Alkali metals

ii)Halogens

Give the general group study of hydrogen with reference

i) valence electrons (ii) burning iii) reducing power.

Compare hydrogen and halogens on the basis of :

i) Physical state

ii) ion formation

iii) valency

(iv) reaction with oxygen

Which metal is preferred for the preparation of hydrogen

(i) from water?

(ii) from acid?

(i) Write the reaction of steam with a red hot iron.

(ii) Why is this reaction considered a reversible reaction?

(in) How can the reaction proceed continuously?

Complete the following word equations

(a) Sodium hydroxide + zinc -4 hydrogen ……. . …………..

b) Calcium + water —9 calcium hydroxide + ………………….

a) Name the impurities present in hydrogen prepared in the laboratory.

b) How can these impurities be removed?

Which test should be made before collecting hydrogen in a gas jar?

Hydrogen is manufactured by the ‘Bosch Process’.

(a) Give the equations with conditions.

(b) How can you obtain Hydrogen from a mixture of Hydrogen and carbon monoxide?

Thin strips of magnesium, copper, and iron are taken. (a) Write down what happens when these metals are treated as follows

(i) Heated in presence of air

(ii) Heated with dil. HCI Added to an aqueous solution of zinc sulfate

(iii) Added to an aqueous solution of Zinc sulphate

(b) Arrange these metals in descending order of reactivity.

Give a reason for the following

a) Zinc granules are used in the laboratory preparation of Hydrogen.

b) Purified and dry Hydrogen is collected over Mercury.

c) The end of the thistle funnel should be dipped under acid.

d) Dilute Sulphuric acid cannot be replaced by concentrated acid in the preparation of Hydrogen.

a) Where does Hydrogen occur in a free state?

b) How did the name Hydrogen originate

Hydrogen can be prepared with the help of cold water. Give a reaction of Hydrogen with:

a) a monovalent metal b) divalent metal

Which metal is preferred for collecting Hydrogen from

a) Coldwater

b) Hot water

c) Steam

Hydrogen may be prepared in the laboratory by the action of a metal on an acid.

(a) Which of the metals copper, zinc, magnesium, or sodium would be the most suitable?

(b) Which of the acids dilute sulphuric, concentrated sulphuric, dilute nitric, and concentrated nitric would

Do you choose?

Explain why you would not use the acids you reject.

(c) How would you modify your apparatus to collect dry hydrogen? Which drying agent would you employ

for this purpose?

Why are the following metals not used in the lab? preparation of hydrogen?

(a) calcium (b) iron (c) aluminium (d) sodium

Based on the reactions of water on metals. arrange the following metals in increasing order of reactivity.

Iron, sodium magnesium, zinc, calcium

Hydrogen is evolved when dilute HCl reacts with magnesium, but nothing happens in the case of

mercury and silver. Explain.

Steam can react with a metal and a nonmetal to liberate a product similar to liberate Hydrogen. Give

necessary conditions

and equations for the same

Hydrogen is obtained by displacement from

a) dilute sulphuric acid

(b) dilute hydrochloric acid

Write equations using zinc and Iron.

Why does not copper show similar behavior?

Give a reason for the following

a) Though lead is above hydrogen in the activity series, it does not react with dilute hydrochloric acid or dilutes sulphuric acid.

(b) Potassium and sodium are not used for reaction with dilute hydrochloric acid or dilute sulphuric acid in the laboratory preparation of hydrogen

If the following are kept in closed vessels at over 4000c what would happen to them?

(a) iron filings and steam,

(b) hydrogen and magnetic oxide of iron?

a) Metal in the powdered form reacts very slowly with the boiling water, but it decomposes steam.

Name the metal.

b) Write a balanced equation for the reaction of the named metal with (i) boiling water (ii) steam

What do you observe when hydrogen gas is passed through a soap solution ?

Under what conditions can hydrogen be made to combine with

(a) nitrogen ? (b) chlorine ? (c) sulphur ? (d) oxygen `?

Name the products in each case and write the equation for each

When hydrogen is passed over a black solid compound A, the products are ‘a colorless liquid’ and ‘a

reddish-brown metal B.’

Substance B is divided into two arts, each placed in separate test tubes.

Dilute HC1 is added to one part of substance B and dilute HNO3 to the other.

(a) Name the substances A and B. (b) Give two tests for the colorless liquid formed in the experiment.

(c) What happens to substance A when it reacts with hydrogen ? Give reasons for your answer.

(d) Write an equation for the reaction between hydrogen and substance A.

(e) Is there any reaction between substance B and dilute hydrochloric acid ? Give reasons for your answer.

Describe briefly the ionic concept of oxidation and reduction. Give an equation to illustrate

Is it essential that oxidation and reduction must occur side by side in a chemical reaction? Explain.

State, giving reasons, whether the substances printed in bold letters have been oxidized or reduced.

(a) Pb0 + CO –> Pb + CO2

(b) Mg + 2HC1 —-> MgC12 + H2

(c) H2S + C12 –> 2 HCl + S

(d) C12 + H2S –> 2HC1 + S

State whether the following conversions are oxidation or reduction reactions.

(a) Pb02 + SO2 –> PbSO4

(b) Cu2+ + 2e -> Cu

(c) K -> K+ + e-

(d) 2C1- — 2e- —> C12

In the following reaction : A+ + B –>A + B. Write half reactions for this reaction and name :

(a) oxidizing agent (b) substance oxidized (c) reducing agent.

Divide the following redox reactions into oxidation and reduction half reactions.

(i) Zn + Pb2+ –> Zn2+ + Pb

(ii) Zn + Cu2+ —> Zn2+ + Cu (iii) C12 + 2Br → Br2+ 2Cl-

(a) Write the equation in the ionic form

CuSO4 (aq) + Fe (s) → FeSO4 (aq) + Cu (s)

(b) Divide the above equation into oxidation and reduction half-reactions

Give reasons

(a) Hydrogen is collected by the downward displacement of water and not of air, even though it is lighter than air.

(b) A candle brought near the mouth of a jar containing hydrogen gas starts burning but is extinguished when pushed inside the jar.

(c) Apparatus for laboratory preparation of Hydrogen should be airtight and away from a naked flame

Select the odd one out and justify your atiswv

(a) Zn, Fe, Mg, and Na

(b) SO2. H2S, NH3, and CO2

(c) Fe, Zn, Cu, and Mg

(d) Fe. Pb, Al, and Zn

(a) Helium is preferred to hydrogen for filling balloons because it is

(i) lighter than air (ii) almost as light as hydrogen (iii) non-combustible (iv) inflammable

(b) Reacting with water, an active metal produces

(i) oxygen

(ii) nitric acid

(iii) a base

(iv) none of these.

(c) A metal oxide that is reduced by hydrogen is

(i) A12O3

(ii) CuO

(iii) Cao

(iv) Na2O

(d) Which of the following statements about hydrogen is incorrect `?

(i) It is an inflammable

gas

(ii) It is the lightest gas.

(iii) It is not easily liquefied.

(iv) It is a strong oxidizing agent.

(e) For the reaction PbO + H2 → Pb + H2O, which of the following statements is wrong?

i) H2 is the reducing agent. (ii) PbO is the oxidizing agent. (iii) PbO is oxidized to Pb (iv) H2 is oxidized to

H2O.

f) Which metal gives hydrogen with all of the following: water, acids, alkalis?

(i) Fe

(ii) Zn

(iii) Mg

(iv) Pb

(g) Which of the following metals does not give hydrogen with acids?

(i) Iron (ii) Copper

(iii) Magnesium (iv) Zinc

Choose terms from the options given in brackets to complete these sentences.

(a) When CuO reacts with hydrogen, …………… is reduced and …………… is oxidized to ……………

(CuO, H2, Cu, H2O)

(b) Hydrogen is …………… soluble in water. (sparingly, highly, moderately)

(c) Metals like …………… H, with steam. • • • • • • • • • • • • • • • and • • • • • • • • • • • • • • • give

(iron, magnesium, aluminum, sodium, calcium)

(d) Sodium reacts smoothly with cold water. (metal, amalgam, in the molten state)

(e) A metal ………….., hydrogen in the activity series gives hydrogen with …………… acid or ……… (above,

below ………acid. dilute hydrochloric, concentrated hydrochloric, dilute sulphuric).

Correct the following statements

(a) Hydrogen is separated from CO by passing the mixture through caustic from solution.

(b) All metals react with acids to give hydrogen.

(c) Hydrogen is dried by passing it through conc H2SO4.

(d) Very dilute nitric acid reacts with iron to produce hydrogen.

(e) Conc. H2SO4 reacts with zinc to liberate hydrogen

Name (a) an oxidizing agent that does not contain oxygen.

(b) a substance that oxidizes concentrated HCl to chlorine.

(c) a substance that will reduce aqueous Iron (III) ions to iron (II) ions.

(d) a liquid that is an oxidizing as well as a reducing agent.

(e) a gas that is oxidizing as well as a reducing agent.

(f) a solid that is an oxidizing agent