1 D and F Block Elements
A reagent used to test the presence of Fe+2 ion is :
1) NH4CNS 2) H2S 3) K3Fe(CN)6 4) K4Fe(CN)6.
2 Classification of Elements and Periodicity
Successive ionization potentials of a metallic element 'M' are 520 kJ, 7300 kJ, 10100 kJ, 13500 kJ respectively. Identify the formulae of compounds when it combines with non-metals X and Y. 'X' contains 7 electrons in valence 'M' shell and 'Y' contains 6 electrons in valence 'N' shell. 1) M2X, MY 2) MX2, MY2 3) MX, MY 4) MX, M2Y
SOLUTION
The IE2 is very high compared to IE1
. Thus M attains inert gas configuration on removal of 1 electron
Hence its valency is 1. Valency of X is 1 as it needs 1 electron to complete its octate and similarly valency of Y is 2. Thus M forms MX and M2Y
3 Biomolecules
Ribose is an example of a/an: 1) aldopentose. 2) ketohexose. 3) aldohexose. 4) disaccharide.
4 Ionic Equilibrium
Which of the following salts on dissolution of water gives pH less than 7 at 250C?
1) KCN. 2) CH3COONa 3) NaBr 4) NH4Cl
Solution:
As NH4Cl is a salt of strong acid and weak base, it's pH will be less than 7 since the salt is acidic in nature.
5 Hydrogen
Silver reacts with hydro chloric acid to give
1) AgCl 2) H2 3) AgH 4) no reaction
Silver cannot replace H from HCl as it is placed at bottom of H in reactivity series, hence less reactive then H.
6 Ionic Equilibrium
pKa value for acetic acid at the experimental temperature is 5. The percentage hydrolysis of 0.1M sodium acetate solution will be
1) 1×10−4 2) 1×10−2 3) 1×10−3 4) 1×10−5
pKa=5
, so Ka=1×10−5
α=√ (Ka /C)
= 1×10−2
7 S – Block Elements
30 g of Magnesium and 30 g of oxygen are reacted, then the residual mixture contains:
1) 50 g of Magnesium oxide and 10 g of oxygen 2) 40 g of Magnesium oxide and 20 g of oxygen 3) 45 g of Magnesium oxide and 15 g of oxygen 4) 50 g of Magnesium only
2Mg + O2 → 2MgO2
According to the above reaction,
28.6g(2mole) Mg Mg combine with 32g(1mole) of O2 to give 80.6g(2mole) of MgO.
thus,
30g Mg will combine with 20g of O2 to produce 50g MgO and 10g O2 will remain unreactive.
8 S – Block Elements
Which of the following is used as a sources of hydrogen for filling of balloons that is convenient and can be carried around?
1) Lithium hydride 2) Sodium borohydride 3) Calcium metal 4) Sodium formate
9 Purification and Characterisation of Organic Compounds
The techniques of gas liquid chromatography is suitable for compounds which are?
1) Soluble in water
2) Highly volatile
3) Vaporise without decompostion
4) Liquids
Among the various types of gas chromatography, gas-liquid chromatography is the method most commonly used to separate organic compounds.
It follows the principle of partition. It can be used for compounds which vaporize without decomposition.
10 S – Block Elements
Which of the following is not an ingredient of clinker cement?
1) Calcium silicate 2) Aluminium silicate 3) Calcium aluminium silicate 4) Gypsum
The four main components of clinker are:
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