Assertion (A) : Sodium metal is stored under kerosene.
Reason (R) : Metallic sodium melts when exposed to air.
(a) Both A and R are true and R is the correct explanation of A
(b) Both A and R are true but R is not the correct explanation of A
(c) A is true but R is false
(d) A is false but R is true
(c) Sodium metal is generally kept inside kerosene oil because of its extreme reactive nature. In open air it reacts violently and burns vigorously to form sodium oxide .
2. Assertion (A) : To dilute sulphuric acid, acid is added to water and not water to acid.
Reason (R) : Specific heat of water is quite large.
(a) Both A and R are true and R is the correct explanation of A
(b) Both A and R are true but R is not the correct explanation of A
(c) A is true but R is false
(d) A is false but R is true
(a) Sulphuric acid (H2SO4) reacts very vigorously with water, in a highly exothermic reaction. Thus if you add water to concentrated sulfuric acid, it can boil and you may get a nasty acid burn. That's why for dilution, acid is added to water not water to acid as specific heat of water is quite large and it can absorb large quantity of heat produced by sulphuric acid. Moreover water is less dense than sulphuric acid, so if you pour water on the acid, the reaction occurs on top of the liquid. If you add the acid to the water, it sinks and any wild and crazy reactions have to get through the water or beaker to get to you.
3. Match List-I (Naturally occurring substances) with List-II (Elements) and select the correct answer using the codes given the lists:
List-I List-II
A Diamond 1. Calcium
B. Marble 2. Silicon
C. Sand 3. Aluminium
D. Ruby 4. Carbon
Codes:
(a) A-3; B- 1; C-2; D-4
(b) A - 4; B- 2; C- 1; D-3
(c) A-2; B- 1; C-3; D-4
(d) A - 4; B- 1; C- 2; D-3
(d) Diamonds is the polymorph of the element carbon. Calcium is the basic element of naturally occuring marble. Sand is formed by Silicon and Aluminium is the basic element of naturally occuring Ruby.
4. Match List-I with List-II and select the correct answer using the codes given below the lists:
List-I List-II
A. German silver 1. Tin
B. Solder 2. Nickel
C. Bleaching powder 3. Sodium
D. Hypo 4. Chlorine
Codes:
(a) A-1; B-2; C-4; D-3
(b) A-2; B-1; C-3; D-4
(c) A-1; B-2; C-3; D-4
(d) A-2; B-1; C-4; D-3
(d) German silver has a color resembling silver, but is an alloy of primarily copper, nickel and zinc. Solder is an alloy of tin, antimony, copper and lead. Bleaching powder contains calcium chloride and calcium hypochlorite, used in solution as a bleach. Bleaching powder is sold on the basis of available chlorine, which is liberated when it is treated with a dilute acid. It is used for bleaching paper pulps and fabrics and for sterilizing water. Hypo solution used in iodometric titration is sodium thiosulphate (Na2S2O3).
5. Which one of the following materials is very hard and very ductile?
(a) Carborundum
(b) Tungsten
(c) Cast iron
(d) Nichrome
(d) Nichrome is a non-magnetic alloy of nickel, chromium, and iron, usually used as a resistance wire. A common alloy is 80% nickel and 20% chromium, by mass. This alloying provide nichrome properties like hardness and ductility.