PYQ - 5 Marks

Answer 1-
(i) When A magnesium ribbon is burnt in air
2Mg(s) + O2(g) → 2MgO(s): Combination Reaction
(ii) When Limestone is heated
CaCO3(s) → CaO(s) + CO2(g): Thermal Decomposition Reaction
(iii) When Silver bromide is exposed to sunlight
2AgBr(s) → 2Ag(s) + Br2: Photolytic Decomposition Reaction
(iv) When Electricity is passed through acidified water
2H2O(l) → 2H2(g) + O2(g): Electrolytic Decomposition reaction
(v) When Ammonia and hydrogen chloride are mixed with each other.
NH3(g) + HCl(g) → NH4Cl(s): Combination Reaction

PYQ - 3 Marks

Answer 2-
(i) The test tube becomes cooler during the reaction because
the reaction is endothermic (absorbs heat from
surrounding).
(ii) During the reaction, heat is absorbed. Hence, this reaction is
an endothermic reaction. These reactions cause a cooling
effect by lowering the temperature of their surroundings.
(iii) The balanced chemical equation of the reaction involved is
as follows: Ba(OH)2 + 2NH4Cl + Heat → BaCl2 + 2NH3 + 2H2O

PYQ - 5 Marks

Answer 3-
a. Zygote is formed by the fusion of male and female gamete.
b. Placenta is a special tissue through which the developing embryo/foetus gets nutrition from mother’s blood. It also transports wastes of the embryo into mother’s blood.
c. Ovulation releases mature ovum from ‘ the ovary. It happens once during a menstrual cycle that is for roughly 28 days.
d. STDs caused by bacterial infection are Gonorrhoea and Syphilis.
e. Prenatal sex determination is misused and it may be the reason for female foeticide.