FRANK Solutions for Class 9 Chemistry Chapter 9 - Study of the First Element - Hydrogen
Chapter 9 - Study of the First Element - Hydrogen Exercise 146
(b) What is the difference between 2H and H2?
(c) Who gave hydrogen its name and why?
(b) 2 H means 2 atoms of hydrogen while H2 means one molecule of hydrogen.
(c) Lavoisier gave "Hydrogen" its name because it means water product.
1.In free state, it is found in traces in the earth's crust and atmosphere. On the sun and bright stars, hydrogen is very abundant.It is suggested that the source of sun's energy is fusion of hydrogen to helium.
2.In combined state it is found in the compounds like water, acids, organic materials and minerals. Natural gas coming out from oil wells, coal mines and volcanoes invariably contains this gas.
(i) Electronic configuration-Hydrogen as well as alkali metals have one electron in their valence shell.
H (1) = 1 ; Li(3)= 2, 1 ; Na(11) =2, 8, 1
(ii) Ion formation-Hydrogen loses one electron to form H+ ion like the alkali metals which form Li+, Na+, K+ etc.
(iii) Valency electrons-Like alkali metals, hydrogen exhibit valency of one in its compounds , as it has only one electron in its outermost shell.
(iv) Combination with non-metals-Like alkali metals, hydrogen combines with non-metals such as oxygen, chlorine and sulphur forming their oxides, chlorides and sulphides respectively.
(v) Reducing action-Like alkali metals, hydrogen is also a very good reducing agent.
(i) Electronic configuration-All the halogens have seven electrons in their outermost shell and need just one more electron to attain stable inert gas configuration. Similarly, hydrogen with one electron in its outermost shell requires one electron to attain a stable inert gas(Helium) configuration.
(ii) Valency-Hydrogen and halogen both show a valency of one.
(iii) Non-metals-Hydrogen is non-metallic like halogen.
(iv) Atomicity-Hydrogen as well as halogens are diatomic gases, e.g.H2,Cl2.Br2 etc.
(v) Ion formation-Halogens have a strong tendency to gain an electron to form halide ions.In similar way, hydrogen shows tendency to gain one electron to form hydride ion (H-).
(i) Reactants used
(iv) Complete labelled diagram
(v) Method of selection
(vi) Drying agent for gas
have following impurities-
(i) Hydrogen sulphide (H2S),
(ii) Sulphur dioxide (SO2),
(iii) Oxides of nitrogen,
(iv) Phosphine (PH3),
(v) Arsine (AsH3),
(vi) Carbon dioxide, Nitrogen oxides,
(vii) Water vapour
They are removed by passing through-
(i) Lead nitrate solution-It absorbs H2S.
(ii) Silver nitrate solution (AgNO3)-It absorbs PH3, AsH3
(iii) Caustic potash (solid KOH)-It absorbs CO2, SO2, oxides of nitrogen
(iv) Anhydrous calcium chloride or P2O5-It absorbs moisture.
(b) Which of the following metal oxides cannot be reduced to metal by hydrogen?
CuO, Ag2O, MgO, PbO
(ii) Describe briefly, with equations, the Bosch Process for the large scale production of hydrogen.
(iii) Account for the following facts:
(a) Though lead is above hydrogen in the activity series, it does not react with dilute hydrochloric acid or dilute sulphuric acid.
(b) Potassium and sodium are not used to react with dilute hydrochloric acid or dilute sulphuric acid in the laboratory preparation of hydrogen.
Chapter 9 - Study of the First Element - Hydrogen Exercise 147
(b) Why is copper not used to prepare hydrogen by the action of dilute HCl or dilute H2SO4 on the metal?
(a) Write down what happens when the metals are treated as follows:
(i) When each metal is heated.
(ii) When each metal is heated with dilute HCl.
(iii) When each metal is added to an aqueous solution of zinc sulphate
(b) Arrange these metals in the descending order of their activities.
(a) Vegetable oil can be changed into a solid by the use of a ______ catalyst and the ______ element.
(b) A metal ______ hydrogen in activity series gives hydrogen with ______ acids.
(c) Hydrogen form ______ bonds with strongly ______ elements.
(d) When CuO reacts with hydrogen, ______ is reduced and ______ is oxidised to ______.
(e) Water gas is a mixture of ______ and ______.
(f) Hydrogen gas is liberated by the action of aluminium with concentrated solution of ______.
(g) The hydrogen at the moment of its formation is called ______.
(h) When hydrogen burns ______ is produced.
(b) above, dilute mineral
(c) covalent, electronegative
(d) CuO, hydrogen, water
(e) CO, H2
(g) nascent hydrogen
(a) Hydrogen gas is easily liquefiable.
(b) Hydrogen is combustible as well as supporter of combustion.
(c) Anhydrous calcium chloride is used to dry hydrogen gas.
(d) The reaction between hydrogen and oxygen is exothermic.
(e) Zinc gives hydrogen when reacted with dilute HCl and conc. NaOH.
(f) The position of hydrogen is not fixed in periodic table.
(g) Magnesium with very dilute HNO3 produces hydrogen.
(h) Occluded hydrogen is less active than ordinary hydrogen.
(a) Hydrogen is collected by the downward displacement of water and not by air,even though it is lighter than air.
(b) Apparatus for the laboratory preparation of hydrogen should be air tight and away from the flame.
(c) Nitric acid and hot concentrated H2SO4 are not used in the preparation of hydrogen.
(d) A large piece of sodium should not be placed in water.
(e) Na, K and Ca cannot be used to prepare hydrogen from acids.
(f) In the laboratory preparation of hydrogen zinc granules are preffered over pure zinc metal.
(g) In Bosch process, steam should not be passed over white coke for a long time.
(h) When a burning splinter is introduced into a jar of hydrogen, the splinter gets extinguished.
(i) Hydrogenated vegetable fats are not advised to be used in preparation of foodstuffs.
(j) Though hydrogen is the lightest element it is not used in weather ballons.
(k) Lead is not used to prepare hydrogen from acids.
Chapter 9 - Study of the First Element - Hydrogen Exercise 148
(a) passed over heated copper oxide.
(b) passed over heated sodium.
(c) Nascent hydrogen
Observation: The reaction takes place at room temperature even without heating. A brisk effervescence with the evolution of gas is seen inside the bottle.
If burning candle is brought near the bubbles of hydrogen gas, they explode.This proves that bubbles were full of hydrogen gas and they move up in the air because they are lighter than air.
(a) meteorological balloons
(b) in metallurgy
(c) in fuel
(d) in making fertilizers
(b) In metallurgy - Hydrogen acts as a very good reducing agent. It is used to obtain metals by reducing their oxides.
(c) In fuel - Hydrogen has very high heat of combustions, therefore it is used as fuel in the form of coal gas, water gas and liquid hydrogen(for rocket propulsion).
(d) In making fertilizers - A large quantity of hydrogen is used in the manufacture of ammonia by Haber process. Ammonia is used in manufacture of HCl and methyl alcohol.
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