BITSAT Chemistry Test - 9 - JEE MCQ

CH₄ has a regular tetrahedral geometry, so it has zero dipole moment. Again all the C-H bonds are identical. PH₃ has pyramidal geometry while NH₄⁺ is polar due to presence of +ve charge.

Lyophilic sols are more stable due to the fact that lyophilic colloids are extensively solvated, which means the colloidal particles are covered by a layer of dispersion medium.

In diamond, each carbon is bonded covalently to four other carbon atoms by sp³ hybridisation. In graphite, each carbon atoms is linked to three other carbon atom by sp² hybridisation. In acetylene, there is sp hybridisation.

Some of the oxygen molecules dissociate when silent electric discharge is passed. Then atomic oxygen combines with oxygen molecules.

Energy is absorbed in this reaction.

Lipids are constituents of plants and tissues. They include fats, oils, carbohydrates, phospholipids, wax, steroids etc. and mainly made up of carbon, hydrogen and oxygen.These are ester class of compounds, while amino acids do not belong to lipids.

The electropositive character of alkaline earth metal increases down the group, therefore, larger alkaline earth metals are able to form ions more easily. So the ionic character of chlorides of these metals increases down the group.
i.e.,BaCI₂ < MgCL₂ < CaCI₂ < BeCI₂ (Ionic character)

A sudden large jump between the values of 2nd and 3rd ionisation energies of an element indicates, that the element has two-electrons in its valence shell. Then the possible electronic configuration may be-----> 1s², 2s², 2p⁶, 3s²

Etard reaction -Chromium chloride dissolved in CCL₄ is made to react with toluene and product formed is decomposed with water.

When H₂ gas is passed through a solution of acetyl chloride in xylene in presence of Pd and BaS0₄ poisoned by sulphur acetaldehyde is formed. This reaction is called as Rosenmund’s reduction reaction.

It cannot be prepared by the direct reaction of Be and F₂ because of high ionisation and atomisation enthalpy of Be.
Be cannot replace Li.
So, the best route is the thermal decomposition of  (NH₄)₂BeF₄
Thermal decomposition of (NH₄)₂BeF₄
(NH₄)2[BeF₄]→2NH₄F+BeF₂

3Mg + N₂ →Mg₃N₂
Mg₃N₂ + 6H₂O→3Mg(OH)₂ + 2NH₃

Be < Mg < Ca < Sr < Ba. The size of the ion is very big (approx. 3Å). Therefore, as the size of the cation increases, their hydration energies decrease more rapidly than their lattice energies. Consequently, the solubilities of sulphates decrease down the group.

The chemical formula of Plaster of Paris is While the chemical formula of gypsum is CaSO₄.2H₂O

In the periodic table, the elements are arranged in increasing order of their atomic numbers.
As we move from top to bottom in the periodic table, the atomic number of the elements increases.
By this definition, the atomic number increases in the order Li⁺ < Na⁺ < K⁺ < Cs⁺.
As we move from top to bottom in the periodic table, the ionic radius of elements keeps on increasing. This is because as one electron is removed from the valence shell of the atom, the effective nuclear charge on the valence shell decreases. Thus, ionic radius increases.
Therefore, the ionic radius of Cs⁺ is the largest.

When H₂O reacts with KO₂, it liberates oxygen.
2KO₂+H₂O→2KOH+H₂O₂+ 1/2 O₂
Whereas, others do not liberate oxygen when react with H₂O.
NaOH gets dissolved in water.
BeO does not react with water due to its covalent nature.
Li₂O dissolves in water to make lithium hydroxide.

Most alkali metals glow with a characteristic colour when placed in a flame.
The energy of the flame causes excitation of the outermost electron, which on return to its ground state releases energy, which falls in the visible region.
The frequency of the light emitted is observed to increase with respect to:

The energy released will be increasing from Li⁺ to Cs⁺
As the size of Cs is large, it requires the least amount of energy to excite the electrons. Hence, it releases high energy radiation because the colour emitted is complementary to colour absorbed.
Since energy released is high, the wavelength of light emitted in the flame will be least for caesium.
The colours so exhibited by the flames will be: lithium shows crimson red, sodium is a golden yellow, potassium is pale violet, rubidium is a red-violet and caesium emits blue.

The solubility of an ionic compound depends on two factors :
(a) Lattice energy, and (b) Hydration energy

In case of alkaline metal hydroxides, the lattice energy decreases as we move down the group. This decrease is more than the decrease in the hydration energy down the group.

When sodium is heated in air at 300°C, it forms sodium peroxide (Na₂O₂).

This sodium peroxide reacts with CO₂ to give Na₂ CO₃ and O₂.

According to Graham's law of diffusion, rate of diffusion of the gas is inversely proportional to the square root of the molecular mass.

Relative rates of diffusion if two gases.

P_A and P_B are partial pressures at which they are diffusing.

According to Clausius-Clapeyron, if a graph is plotted between a straight line is obtained with negative slope.

Van der Waals' equation (for one mole):

at low pressure V_m will be high in comparison to the volume of molecules as the molecules will be quite apart to each other and thus empty space is large.
 'b' can be neglected 

PV = RT

This can also be derived from Euler's chain rule in Mathematics.

At constant P and V,
n₁T₁=n₂T₂
4T₁=3.2(T₁+50)
On solving,
T₁=200K

Dalton's law of partial pressure is not applicable to gases which react chemically and produce different number of moles of products than the reactants. Some gases which do not obey this law are
SO₂+Cl₂, CO+Cl₂, NO+O₂, NH₃+HCl and H₂ + Cl₂

Given, V1=200 cm³, P1=1 atm
V₂=50 cm³, P₂=?
Boyle's law states that the pressure exerted by a gas is inversely proportional to its volume at a constant temperature. According to Boyle's law,
P₁V₁=P₂V₂
1×200=P₂×50

A → 3B
At t = 0, 2 atm
At t = 20; 2 - x + 3x
2 - x + 3x + 2 = 6 ⇒ x = 1
Applying k = we get
t_75% = 40 min

Clean water has BOD value less than 5 ppm. The BOD value more than 5 ppm indicates the polluted water. The excessive growth of algae and aquatic plants due to the presence of plant nutrients is called eutrophication. The decomposition of these aquatic plants utilises the dissolved oxygen, which proves fatal for aquatic animals.