ICSE Set Qa1 Year Icse Chemistry99 Qa1.php Chemistry Exam Paper for students online

Chemistry - 1999( I.C.S.E)
You are on answer 1 of Set I
 

SCIENCE
SECTION - A (40 Marks)

Q.1 (a) Chlorine is the subject of the following questions :
(i) What is the atomicity ?
(ii) Name the compounds formed when chlorine react with water.
(iii) Chlorine reacts with white phosphorus forming phosphorus trichloride and phosphorus pentachloride . Write balanced equation for the formation of each of these compounds.
Ans. 1(a)(i) 2
(ii) Hydrochloric acid and hypochlorus acid.
(iii) P₄ + 6Cl₂ ¾® 4PCl₃
P4 + 10Cl₂  ¾® 4PCl₅

Q.1(b) Answer the following questions, relating your answer only to salts in the list given below:
Anhydrous calcium chloride, copper sulphate-5-water, sodium carbonate-10-water.
(i) Which compound is efflorescent ?
(ii) Which compound is blue in colour ?
(iii) Which compound is deliquescent ?
(iv) What would be seen in mixing a solution of calcium chloride with a solution of sodium carbonate ?
(v) Write a balanced equation for the reaction occurring when a solution of calcium chloride is mixed with a solution of sodium carbonate.
Ans.1 (b)(i) Sodium carbonate - 10 - water.
(ii) Copper sulphate - 5 - water.
(iii) Anhydrous calcium chloride.
(iv) White ppt.
(v) CaCl₂ + Na₂CO₃ ¾® 2NaCl + CaCO₃

Q.1(c) In this question you are required to supply the word (or words) that will make each  sentence in to a correct statement which to be written down in full.
Example: sodium reacts with chlorine to form sodium chloride.
Answer:  Molten sodium reacts with chloride to form sodium chloride.
(i) The electrolysis of lead bromide liberates lead and bromine.
(ii) Copper sulphate crystals are dehydrated by sulphuric acid.
(iii) Calcium nitrate reacts with sodium sulphate to form calcium sulphate. (same word is required in two places.)
(iv) Crystals of sulphur are obtained when a solution of sulphur in carbon disulphide is allowed to evaporate.
Ans. 1(c)(i) Molten lead bromide.
(ii) Hydrated copper sulphate is dehydrated by conc. sulphuric acid.
(iii) Sodium nitrate.
(iv) Crystals of Rhombic sulphur.


Q.1(d) If a crop of wheat removes 20 kg of nitrogen per hectare of soil, what mass of the fertilizer calcium nitrate Ca(NO₃)₂ would be required to replace the nitrogen in a 10-hectare field ? (N = 14; O = 16; Ca = 40. Answer to the nearest kg.)
Ans.1 (d) Total nitrogen required by 10 hectares = 10 x 20 = 200 kg.
Ca(NO₃)₂ N₂
         or
164 parts of Ca(NO₃)₂ gives 28 gm of N₂
Now 28 parts of N₂ 164 parts of Ca(NO₃)₂
200 parts of N₂ (164 x 200) / 28
= 1171.4 kgs.

Q.1(e)(i) A vessel contains N molecules of oxygen at a certain temperature and pressure. How many molecules of sulphur dioxide can the vessel accommodate at the same temperature and pressure ?
(ii) Each of two flasks contains 2.0 g of gas at the same temperature and pressure. One flask contain oxygen and the other hydrogen.

1. Which sample contains the greater number of molecules ?

2. If the hydrogen sample contains N molecules, how many molecules are present in the oxygen sample ? (H = 1; O = 16.)

(iii) A gas sample occupies 4 litres at 27⁰C and P atmospheric pressure. What would be its volume at 327⁰C and 2P atmospheric pressure ?
Ans. 1(e)(i) According to Avogadro's law equal volumes of all gases under similar condition of temp and pressure contain equal no. of molecules. Same no. of molecules i.e. N' molecules.

(ii) (1)32 gms of O₂ = 6.023 x 10²³ molecules of O₂
                           6.023 x 10²³ x 2
2 gms of O₂ =  ^{________________________}
                                       32

= 1/16 x 6.023 x 10²³
= 0.376 x 10²³
= 3.76 x 10²² molecules of oxygen
2 gms of H₂ = 6.023 x 10²³ molecules of H₂
= 6.023 x 10²³ molecules of H₂
molecules of H₂ are more than O₂

(ii) (2) Ratio of molecules of O₂ to H₂ is = 1/16 or 1 : 16
therefore Oxygen molecules = N/16

(iii) V1 = 4 litres
V2 = ?
T1 = 300 K
T2 = 600 K
P1 = P
P2 = 2P
P1 V1 / T1  = P2 V2 / T2
P x 4 / 300 = 2P x V2/600
V2 = (P x 4 / 300 ) x (600 / 2P)
= 4 liters

Q.1(f) Describe, in each case, one chemical test that would enable you to distinguish between the following pairs of chemicals. Describe what happens with each chemical or state no 'visible reaction'.
(i) sodium chloride solution and sodium nitrate solution ;
(ii) sodium sulphate solution and sodium chloride solution ;
(iii) calcium nitrate solution and zinc nitrate solution;

Ans1.(f) (ii)

Sodium Sulphate	Sodium Chloride
(Test of SO4=) Prepare a solution of this chemical in water Add Barium Chloride solution. White ppt. is produced which are insoluble in Conc. Hydrochloride Acid. Na2SO4 + BaCl2-- 2NaCl + BaSO4 (white ppt.) (Insoluble in Conc. HCl)	(Test of Cl-)Perform Chromyl Chloride test (as earlier explained) or Add to this solution silver nitrate, White ppt. is formed which is soluble in ammonium hydroxide AgNO3 + NaCl AgCl (white ppt.)

Ans1. (f)(iii)

Q.1(g) Write balanced equations for each of the following reactions :
(i) Magnesium heated in nitrogen ;
(ii) Action of heat on sodium nitrate ;
(iii) Action of heat on copper nitrate ;
(iv) Zinc and dilute sulphuric acid ;
(v) Ethene and hydrogen ;
(vi) Nitrogen monoxide and oxygen.
Ans1 (g) (i) 3Mg + N₂ ® Mg₃N₂ (Magnesium Nitride)

(ii)

(iii)

(iv)

(v)

(vi)

Q2.(a) Choose the Correct word or phrase from the bracket to complete the following sentences :
(i) Ammonium chloride is a soluble salt prepared by ___________ (precipitation, neutralization).
(ii) When ammonium chloride is heated, it undergoes __________ (thermal decomposition, thermal dissociation).
(iii) Heating ammonium chloride with sodium hydroxide produces __________ (ammonia, nitrogen).
(iv) Heating a solution of ammonium chloride and sodium nitrite produces __________ (ammonia, nitrogen).
Ans.2(a)(i) Neutralization
(ii) Thermal decomposition
(iii) Ammonia
(iv) Nitrogen.

Q2.(b) Write the correctly balanced equation for each of the reactions mentioned in statements (i) - (iv) above.
Ans2.(b)

Q2.(c) Describe what you see when concentrated nitric acid is added to copper.
Ans 2.(c)

(But Dry Chlorine gives SO₂ + Cl₂ -- SO₂Cl₂)
(v) Chlorine is an oxidising agent

Q.3(b)(i) What is the purpose of the Contact Process ?
(ii) Name the catalyst used in the Contact Process.
(iii) Write the balanced equation for the reaction in the Contact Process which takes place in the presence of the catalyst.
Ans. 3(b) (i) Purpose of contact process is to prepare H₂SO₄ (Sulphuric Acid)
(ii) vanadium pentoxide
(iii)

Q.3(c)(i) When hydrogen sulphide reacts with oxidizing agents, what substance is always a product of the reaction ?
(ii) What is the colour of the precipitation formed when hydrogen sulphide is bubbled through copper sulphate solution ?
Ans .3 c (i) Sulphur
(ii) Black ppt.

Q.4(b) Write balanced equations for the following reactions :
(i) Reduction of copper oxide by hydrogen.
(ii) Reduction of iron (III) oxide by carbon monoxide.
(iii) Reduction of lead (II) oxide by carbon.
Ans.4(b) (i) CuO + H₂ -- Cu + H₂O
(ii) Fe₂O₃ + 3CO -- 2Fe + 3CO₂
(iii) PbO + C -- Pb + CO

Q.4(c)(i) What is the type of bonding expected in a metallic chloride ?
(ii) If a fused metallic chloride is electrolysed, at which electrode would the metal be obtained ?
(iii) What metallic property is shown by the non-metal graphite ?
Ans 4 (c) (i) Ionic Bond or Electrovalent bond
(ii) At Cathode
(iii)conduction

Q.4(d)(i) Cast iron contains about 4% carbon. By what chemical process is the amount of carbon decreased to make steel ?
Ans 4 (d) (i) Bessemer converter
(ii) Chromium and Nickel

Q5.(a) Concentrated nitric acid oxidises phosphorus to phosphoric acid according to the following equation :
P + 5HNO₃ ¾® H₃PO₄ + H₂O + 5NO₂
(i) What mass of phosphoric acid can be prepared from 6.2 g of phosphorus ?
(ii) What mass of nitric acid will be consumed at the same time ?
(iii) What would be the volume of steam produced at the same time if measured at 760 mm Hg pressure and 273^oC ?
(H = 1; N = 14; O = 16; P = 31)
Ans.5 (a)(i) P + 5HNO₃ --- H₃PO₄ + H₂O + 5NO₂
31 gm of P gives º ( 3+31+64) gm of Phosphoric Acid
98 gm Phosphoric Acid º 31 gm of P
6.2 gm of Phosphoric Acid º (31x6.2) / 98
= 1.96 gms of Phosphorus

(ii) For 98 gms/ H₃PO₄ º 63 x 5 gm/HNO₃ is consumed
For 6.2 gms/H₃PO₄ º (63x5 / 98) x (62 / 10)
= (63x31) / 98
= 19.93 gms of Nitric Acid

(iii) For 98 gms H₃PO₄ º  18 gms of steam
6.2 gms of H₃PO₄ º (18 x 6.2) / 98 gms of steam
º (18 x 62) / (98 x 10)
= 552 / 490 gm/steam
= 1.126 gm/steam

Q.5(b) Ammonia may be oxidized to nitrogen monoxide in the presence of a catalyst according to the following equation :
4NH₃ + 5O₂ ¾® 4NO + 6H₂O
If 27 litres of reactants at the same temperature and pressure ?
Ans 5.(b) 4NH₃ + 5O₂ --- 4NO + 6H₂O
9 volume of reactants gives = 4 volume of No.
27 volume of reactant gives = (4 x 27) / 9
= 12 liters of Nitrogen Monoxide.

(ii) Vinegar

or

(iii) Marsh Gas

Q.6(b)(i) What word is used to describe these three compounds taken together ?
(ii) What is the special feature of the structure of :

(iii) What type of reaction is common to both these compounds ?
Ans 6 (b)(ii) 1. It has a Double covalent bond.
2. It has a Triple covalent bond

Ans 6(b) (iii) Both gives addition reactions.

Q7(a) Define the following terms :
(i) Acid
(ii) pH scale
(iii) neutralization
Ans.7 (a) (i) Acids are those species which field H⁺ (Hydrogen ions) in aqueous solution
(ii) A scale to measure conc. of H+ ion in any solution

If pH value of a solution is lesser than 7, it is Acidic in Nature
If pH value of solution is = 7 it is neutral
If pH is more than 7, it is Basic

(iii) Neutralisation is the process in which H⁺ combine with OH- to form water or Acid react with a base to form salt and water .
HCl(acid) + NaOH(base) --- NaCl(salt) + H₂O

Q.7 (b)(i) Outline the steps that would be necessary to convert insoluble lead (II) oxide into insoluble lead chloride.
(ii) Write the balanced equations for the reactions required to convert insoluble lead (II) oxide into insoluble lead chloride.
(iii) If iron reacts with dilute sulphuric acid, what will be the products ?
(iv) A solution of iron (III) chloride has a pH less than 7. Is the solution acidic or alkaline ?
Ans. 7(b) (i) PbO₂--------PbO+O
PbO+2HCl----------PbCl₂+H₂O   
2HCl+O----------H₂O+Cl₂
PbO₂+4HCl---------PbCl₂+2H₂O+Cl₂

Ans7 (b) (iii) Fe + H2SO₄ -------Fe ₂SO₄ + H₂ (Ferrous Sulphate , Hydrogen)
(b)(iv) A ferric chloride solution has PH less than 7, It is Acidic.