Chemistry Test-32

When a solution of methylene blue is shaken with charcoal, it is observed that the solution becomes colorless.

When charcoal is added to a solution of methylene blue dye the methylene blue dye solution turns colorless as the dye particles are adsorbed on the charcoal surface.

O₂^- (17) Superoxide has one unpaired electron. Since Paramagnetism is shown by those molecules which have at least one unpaired electron, so O₂^- is paramagnetic.

The relationship between the heat supplied, molar heat capacity at constant volume and the temperature change is \(q=m \cdot C_{p} \Delta T\)

\(q=1\) k J \(=1000\) J

Number of moles \(=m=\frac{Mass}{Molecular weight}\)

\(=\frac{100}{18}\)

Substitute values in the above expression:

\(\Rightarrow 1000=\frac{100}{18} \times 75 \times \Delta T\)

So, the temperature change is \(2.4\) K

The elements which have a low value of ionization potential are strong Reducing agents.

The ionization energy is the minimum amount of energy required to remove the most loosely bound outermost electron of an isolated gaseous atom or molecule.Alkali metals have a low value of ionization energy.The ionization energy increases over the period from left to right and decreases down the group.

Since reactivity decreases down the group as the electronegativity of the halogen decreases down the group. Thus, rate of reaction of alkanes with halogens is,

Fluorine is the most electronegative halogen and while going down the group electronegativity decreases. The order of electronegativity is \(\ce{F2 > Cl2 > Br2 > I2}\). As the electronegativity of halogens decreases, their reactivity with alkanes also decreases. Therefore, order of increasing reactivity of halogens with alkanes will be \(\ce{F2 > Cl2 > Br2 > I2}\).

Let \(\mathrm{W}_1\) and \(\mathrm{M}_1\) denote weight and molecular weight of solvent respectively.

Molality \(\mathrm{m}=\frac{\mathrm{n}_2}{\mathrm{~W}_2}\)

Therefore \(\mathrm{n}_2=\mathrm{mW}_1\)

\(\mathrm{x}_2=\frac{\mathrm{n}_2}{\mathrm{n}_1+\mathrm{n}_2}=\frac{\mathrm{mW}_1}{\frac{\mathrm{W}_1}{\mathrm{M}_1}+\mathrm{mW}_1}\)

\(=\frac{\mathrm{mM}_1}{1+\mathrm{mM}_1}\)

\(N _{2} O _{4} \rightarrow 2 NO _{2}\)

at \(t =0\), moles of \(N _{2} O _{4}=1\), moles of \(NO _{2}=0\)

at \(t =\) equilibrium, mole of \(N _{2} O _{4}=1- a\), mole of \(NO _{2}=2 a\)

\(a=\) degree of dissociation.

Molecular weight of mixture \(=\)\(\frac{(1- a ) \times \text { molar mass of } N _{2} O _{4}+2 a \times \text { molar mass of } NO _{2}}{(1- a +2 a )}\)

\(= \frac{(1-0.2)(28+64)+2 \times 0.2 \times(14+32)}{1+0.2}\)

\(M =76.66\)

\(P =1 atm , T =300 K\)

\(d = PM / RT\)

\(=\frac{1 \times 76.66}{0.082 \times 300}=3.11 gm /L\)

The structure of the IF₇ molecule is Pentagonal Bipyramidal.

Iodine (I) is the central metal atom and Fluorine (F) is the monovalent atom. Also, it is a neutral molecule (i.e., the negative and positive charge is zero). In IF₇, the central atom I is attached to 7 fluorine atoms through 7 sigma bonds. So, the steric number is 7 here. Therefore, the hybridization of a central atom in IF₇ is sp³d³.

IF₇ has seven bond pairs and zero lone pairs of electrons.

The rubber obtained is also called Styrene butadiene rubber (SBR). In Buna-S, Bu stands for butadiene and, Na for sodium and S for styrene. It is vulcanised with sulfur. The rubber is slightly inferior to natural rubber in its physical properties.