SECTION -I (40 - Marks)
(One Hour and a Half)
Q 1 (a) Answer the questions below,
relating your answers only to salts in the following list : Sodium
Chloride, anhydrous calcium chloride, copper sulphate - 5- water.
(i) What name is given
to the water in the compound copper sulphate - 5-water?
Ans. (i) Water of Crystalisation
(ii) If copper sulphate -5 - water is heated, the water is driven off
leaving anhydrous copper sulphate.
(A) What is the colour of anhydrous sulphate?
(B) By what means, other
than heating, could you dehydrate copper sulphate -5-water and obtain
anhydrous copper sulphate?
Ans.By heating with any
(iii) What is
Ans.Deliquescence are those substance which absorb moisture such as
anhyd. CaCl2 and NaOH.
(iv) Which one of
the salts in the given list is deliquescent ?
Ans. Anhydrous calcium chloride
Q 1 (b) State what you
see when :
(i) a piece of moist
blue litmus paper is placed in a gas jar of chlorine.
(ii) a piece of moist red litmus paper is placed in a gas jar of
(iii) Silver nitrate solution is added to dilute hydrochloric acid.
(iv) Zinc oxide is heated.
(v) A glowing splint is introduced into a gas jar containing oxygen.
Ans.1 (b) (i) Turns red .
(ii) turns blue
(iii) White ppt of AgCl are formed.
AgNO3 + HCl --------- AgCl + HNO3
(iv) 2ZnO ----------- 2Zn + O2
(v) Glow of splint Increases
Q 1 (c) Write
correctly balanced equations for the following reactions :|
(i) Molten sodium and chlorine.
(ii) Nitrogen and oxygen when lightning strikes.
(iii) Iron and dilute sulphuric acid.
(iv) Decomposition of hypochlorous acid in sunlight.
(v) Action of heat on potassium nitrate.
Ans.1 (c) (i) 2Na + Cl2 ---------- 2NaCl
(ii) N2 + O2 lightning®
2NO (Nitric Oxide)
(iii) Fe + H2SO4(dil) ------------- FeSO4
(iv) HClO ------------------ HCl + O (oxygen)
(v) 2KNO3 ----------------- 2KNO2 +O2
Q 1(d) Water can be
split into hydrogen and oxygen under suitable conditions.
The equation representing the change is :
--------------- 2H2(g) + O2(g).
(i) If a given experiment result in
2500 cm3 of hydrogen being produced, what value of oxygen is
liberated at the same time under the same conditions of temperature and
(ii) The 2500 cm3 of hydrogen is
subjected to 2 1/2 times increases in pressure
(temperature remaining constant ). What volume will the hydrogen now
(iii) Taking the volume of hydrogen
calculated in (d) (ii), what change must be made in the kelvin (absolute)
temprature to return the volume to 2500 cm3 (pressure
Ans.1 (d) 2H2O(e)
------------- 2H2 + O2
(i) 2 Vol. of H2 = 1 vol of O2
(ii) 2500 of H2 = 1/2 x 2500
=1250 cm3 of O2
(iii) (i) P1 = 1 Atm.
P2 = 2.5 Atm.
V1 = 2500
V2 = ?
P1 V1 = P2 V2
1 x 2500 = 2.5 x V2
V2 = 2500x10/25
V2 = 1000 cm3
(iii)(ii) If volume of H2 = 1000
cm3 say, temp. is T1, V2 = 2500 New temp.
V1 / T1 = V2
1000/T1 = 2500/T2
T2 = 2.5 T1
It must be 2.5 times of orignal
Q 1 (e) The compound Na2B4O7.10H2O
is commonly known as borax. When litmus is added to a solution of borax
solution, it turns blue
(i) What can you say about the pH
of borax solution?
(ii) Calculate the precentage of boron (B) in borax. (H = 1, B = 11, O =
16, Na = 23. Answer correct to 1 decimal place. )
Ans 1(e) Borax Na2 B4O7. 10H2O
(i) PH of borax solution is greater than
Basic nature salt of strong Base + weak acid.
% of Boron = 11 x 4 x 100 / 382
= 4400 / 382
= 11.51 %
(ii) BaCl2 + FeSO4
-------------- BaSO4 + FeCl2 (White PPt of
of Barium sulphate are seen )
Q 1 (f) (i) Sodium
hydoxide solution can be used to distinguish between iron (II) sulphate
solution and iron (III) sulphate solution because these solution give
different coloured precipitates with sodium hydroxide solutions. Give the
colour of the precipitate formed with :
(1) Ferrous (II) sulphate solution Feso4+2Nooh
(2) Ferric (III) sulphate solution Fe2(So(So4)
3 + 6 NooH 2Fe(OH)3
(ii) What will you see when barium chloride
solution is addded to iron (II) sulphate solution?
(iii) How will the action of dilute
hydrochloride acid on sodium carbonate and sodium sulphite enable you to
distinguish between these two compounds?
Ans.1 (f)(i) (1)(11 x 4 x
100)/382 (2) = 11.51%
(ii) BaCl2 + FeSO4
BaSO4 + FeCl2
white ppt. of barium Sulphate are seen
(iii) When dilute Hydrochloric acid
is added to sodium carbonate, it gives effervescence due to evolution of
carbon dioxide but sodium sulphite does not do so.
Q. 1(g). Choosing only
words from the following list write down the appropriate words to fill in
the blanks (i) to (v) below :
anions, anode cathode, cations, electrode, electrolyte, nickel, voltameter.
To electroplate an article with nickel
requires an (i) .............................................which must be
a solution containing (ii)...................... ions. The article to be
plated is placed as the(iii).................................. of the cell
in which the plating is carried out .The (iv)............................
of the cell is made from pure nickel. The ions which are attracted to the
negative electrodes and discharged are called (v)
Ans(g) (i) electolyte (ii) Nickel
(iii) anode (iv) Cathode (v) cations
Q 1(h).The following
question result to the Nitrogen Cycle.
(i) What are the soluble
nitrogen compounds absorbed by the roots of plants ?
(ii) What kind of plants directly absorb nitrogen from the atmosphere ?
(iii) What term is applied to the conversion of atmosphere nitrogen to
useful compounds of nitrogen?
(iv) Compounds such as ammonium nitrate. urea and super - phosphate are
used to replace nitrogen and other elements loss from the soil as a result
of cultivation. What is the common name given to these compounds ?
(v) What insoluble substance is used in making superphosphate?
Ans.(h)(i) Nitrates (ii)
Leguminious plants (iii) Nitrogen fixation (iv) fertilizers (v)