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1.Hydrogen can be prepared with zinc by using:
(i)acid
(ii)alkali
(iii)water
give an equation in each case.

Ans. Zn+2HCl9(dil)-->ZnCl2 + H2
(ii) Zn+2NaOH(conc.) -(boil)-> Na2ZnO2 + H2
(iii)Zn+H2O ->ZnO+H2

2.for lab prep. of hydrogen,give the following:
a) material used
b)method of collection
c)chemical equation
d)a fully labelled diagram
Ans. a)material used :
flask, cork, thistle funnel, delivery tube, trough, glass tube and jar, granulated zinc and dil. sulphuric acid.
method of collection :
Downward displacement of water.
chemical equation:
Zn(s)​+H2​SO4(aq)​→ZnSO4(aq)​+H2(g)

A fully labelled diagram.
describe the preparation of hydrogen in the laboratory - Chemistry ...

3 (a)

Write the name of impurities present in hydrogen in lab preparation

(b)

how can you remove it

Ans.HydrogenSulphide,SulphurDioxide, Oxides Of Nitrogen
Phosphine(PH3),CarbonDioxide,
Water Vapour are impurities in hydrogen
b) i)silver nitrate remove PH3 and AsH3
ii)lead nitrate remove H2S
iii) caustic potash solution remove CO2 and SO2

4. which test should be made before collecting H2 in a glass jar?
Ans. some hydrogen gas is collected in test tube and bought near air. if the gas burns quickly it shows there is no more air in flask. the gas is then collected in jar.

5.why nitric acid is not used in preparation of hydrogen?
Ans. because it is a strong oxidising agent and form oxides of nitrogen rather than hydrogen.

6.why hot con. sulphric acid is not used in preparation of hydrogen ?
Ans.because in this case sulphur dioxide is prduced.

7.hydrogen manufactured by bosh process.
a)give the equation with condition.
b)how can u obtain h2 from a mixture of hydroggen and carbon monoxide.
Ans.a)

 b)the mixture can be passed through ammoniacal cuprous chloride.

8. give equation to express the reaction between:
a)Steam and red hot iron.
b)Calcium and water
Ans.a)
what are the chemical properties of heavy metals - Science ...The Chemistry Behind Hydroxide Alkaline Water | Optimal Harmony+hydrogen.

b)
9. a small piece of Ca is put into a small trough containing water . there is effervescece and white tubidity is formed.
a)hydrogen
b) question 8 b part
c)it turns blue
d)the turbidity dis appear and the solution becomes clear.
Ca(OH)2 + 2HCl->CaCl2 + 2H2O

10.thin strips of magnesium, copper and iron are taken.

a)write down what happens when these metals are treated as follows:

i)heated in preasence of air.
ii)heated with dil. HCl

iii)added to an aqueous solution of zinc sulphate,

b)arrange these metals in descending order of reactivity.

Ans. a)1. Heated in the presence of air:
  • All the elements form oxides when they are heated in the presence of air.
  • The equation involved in the reaction is as follows:
M g+O_{2} \rightarrow M g O
F e+O_{2} \rightarrow F e_{2} O
C u+O_{2} \rightarrow C u O
b)
Mg+2HCl\rightarrow MgCl_2+H_2
Fe+HCl\rightarrow FeCl_2+H_2
c)3. Added with an aqueous solution of zinc sulfate:
  • As copper is less reactive than zinc, only magnesium reacts with zinc sulfate and forms the following product.
Mg+ZnSO_4\rightarrow Mg_2SO_4+Zn
b)4. Arrangement of elements bases on decreasing order of reactivity:
  • The given elements when arranged based on descending order of reactivity, it gives
Mg>Fe>Cu.

11. Choose the correct option :
a) Hydrogen is evolved by th e action of cold dil. HNO3
Mg
b) Which metal produces hydrogen gas on reaction with cold water.
Na
c) the composition of the nucleus of deutrium is 
one electron and one neutron
d)Elements which show unique nature in the preparation of hydrogen are
Al,Zn,Pb.

12 Give reasons for the following:
  1. Zinc granules are used in lab preparation of hydrogen.
  2. Purified and dried hydrogen is collected over mercury.
  3. The end of the thistle funnel should be dipped under acid
Dilute sulphuric acid cannot be replaced by concentrated acid in the preparation of hydrogen.
  1. Zinc granules are preferred over pure zinc in the lab preparation of hydrogen because the impurity present in granulated zinc is copper, whose catalysing effect speeds up the rate of the reaction.
  2. Purified and dried hydrogen is collected over mercury because mercury has no reaction with it.
  3. The end of the thistle funnel should be dipped under acid so as to prevent the gas from escaping from the thistle funnel.
  4. Dilute sulphuric acid cannot be replaced by concentrated acid in the preparation of hydrogen because it is a strong oxidising agent and it will produce sulphur dioxide.

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