201.
What happens when magnesium is burnt in air and the products $$X$$ and $$Y$$ are treated with water?
$$X$$
$$Y$$
$$P$$
$$Q$$
(a)
$$MgO$$
$$Mg{\left( {OH} \right)_2}$$
$$Mg{\left( {OH} \right)_2}$$
$${N_2}$$
(b)
$$MgO$$
$$M{g_3}{N_2}$$
$$Mg{\left( {OH} \right)_2}$$
$$N{H_3}$$
(c)
$$MgO$$
$$M{g_3}{N_2}$$
$$Mg{\left( {OH} \right)_2}$$
$${N_2}$$
(d)
$$MgO$$
$$MgC{O_3}$$
$$Mg{\left( {OH} \right)_2}$$
$$C{O_2}$$
A
(a)
B
(b)
C
(c)
D
(d)
Answer :
(b)
202.
A white solid $$X$$ on heating gives a white solid $$Y$$ and an acidic gas $$Z.$$ Gas $$Z$$ is also given out when $$X$$ reacts with an acid. The compound $$Y$$ is also formed if caustic soda is left open in the atmosphere. $$X, Y$$ and $$Z$$ are
$$X$$
$$Y$$
$$Z$$
(a)
$$NaHC{O_3}$$
$$N{a_2}C{O_3}$$
$$C{O_2}$$
(b)
$$N{a_2}C{O_3}$$
$$NaOH$$
$$C{O_2}$$
(c)
$$N{a_2}C{O_3}$$
$$NaHC{O_3}$$
$$C{O_2}$$
(d)
$$NaOH$$
$$NaHC{O_3}$$
$$C{O_2}$$
A
(a)
B
(b)
C
(c)
D
(d)
Answer :
(a)
203. An oxide of alkaline earth metals $$X$$ reacts with $$C$$ and $$C{l_2}$$ to give a compound $$Y.$$ $$Y$$ is found in polymeric chain structure and is electron deficient molecule. The compound $$Y$$ is
A
$$BeO$$
B
$$BeC{l_2}$$
C
$$Be{\left( {OH} \right)_2}$$
D
$$BeC{O_3}$$
Answer :
$$BeC{l_2}$$
204. The recommended concentration of fluoride ion in drinking water is up to $$1ppm$$ as fluoride ion is required to make teeth enamel harder by converting $$\left[ {3C{a_3}{{\left( {P{O_4}} \right)}_2}.Ca{{\left( {OH} \right)}_2}} \right]$$
A
$$\left[ {Ca{F_2}} \right]$$
B
$$\left[ {3\left( {Ca{F_2}} \right).Ca{{\left( {OH} \right)}_2}} \right]$$
C
$$\left[ {3C{a_3}{{\left( {P{O_4}} \right)}_2}.Ca{F_2}} \right]$$
D
$$\left[ {3\left\{ {\left( {Ca{{\left( {OH} \right)}_2}} \right.} \right\}.Ca{F_2}} \right]$$
Answer :
$$\left[ {3C{a_3}{{\left( {P{O_4}} \right)}_2}.Ca{F_2}} \right]$$
205. The metal ion, that plays an important role in muscle contraction, is
A
$$B{e^{2 + }}$$
B
$$M{g^{2 + }}$$
C
$$C{a^{2 + }}$$
D
$$B{a^{2 + }}$$
Answer :
$$C{a^{2 + }}$$
206. In which of the following the hydration energy is higher than the lattice energy ?
A
$$BaS{O_4}$$
B
$$MgS{O_4}$$
C
$$RaS{O_4}$$
D
$$SrS{O_4}$$
Answer :
$$MgS{O_4}$$
207. The order of decreasing ionisation enthalpy in alkali metals is
A
$$Na > Li > K > Rb$$
B
$$Rb < Na < K < Li$$
C
$$Li > Na > K > Rb$$
D
$$K < Li < Na < Rb$$
Answer :
$$Li > Na > K > Rb$$
208.
When kept open in air, the crystals of washing soda lose 9 molecules of water to form a monohydrate. \[N{{a}_{2}}C{{O}_{3}}\cdot 10{{H}_{2}}O\xrightarrow[\text{to}\,\,\text{air}]{\text{exposed}}\] $$N{a_2}C{O_3} \cdot {H_2}O + 9{H_2}O$$
This process is called
A
efflorescence
B
deliquescence
C
dehydration
D
hydration
Answer :
efflorescence
209. In curing cement plasters water is sprinkled from time to time. This helps in
A
developing interlocking needle-like crystals of hydrated silicates
B
hydrating sand and gravel mixed with cement
C
converting sand into silicic acid
D
keeping it cool
Answer :
developing interlocking needle-like crystals of hydrated silicates
210. What is the biological importance of $$N{a^ + }$$ and $${K^ + }$$ ions in cell fluids like blood plasma?
A
They participate in transmission of nerve signals.
B
They regulate the number of red and white blood corpuscles in the cell.
C
They can be present in any amount in the blood since they are absorbed by the cells.
D
They regulate the viscosity and colour of the blood.
Answer :
They participate in transmission of nerve signals.