Chemistry

This is a Multiple Choice Questions as classified in NCERT Exemplar

Option (iii)

For the conversion from Fahrenheit to Celsius

$\mathrm{F}=\frac{9}{5}\mathrm{C}+32$

 On substituting the values in the above equation,

 200 = $\frac{9}{5}C+32$

         =93.3 $°$  C

This is a Multiple Choice Questions as classified in NCERT Exemplar

Ans: option (iv) The two electrons present in the 2s orbital have spin quantum numbers MS but of opposite sign.

According to Pauli's Exclusion Principle no two electrons should possess the same set of four quantum numbers. Thus the two electrons present in the 2s orbital have spin quantum numbers MS but of opposite sign.

This is a Multiple Choice Questions as classified in NCERT Exemplar

Option (ii)

Average of readings of student A,

Average of student A = $\frac{3.01+2.99}{2}=3.00$

Average of readings of student B,

Average of student B = $\frac{3.05+2.95}{2}=3.00$

The correct reading is 3. For both A and B, the average value is close to the correct value. Thus, readings of both are accurate.

The readings of student A are also very close to each other and close to the average value. Thus, readings are precise. Also, the readings of student B are also very close to each other and close to the average value.

This is a Multiple Choice Questions as classified in NCERT Exemplar

Ans: option  (ii)

Fe³⁺, Mn²⁺ Fe³⁺ electronic configuration is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁵ 4s² Mn²⁺electronic configuration is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁵ 4s

This is a Multiple Choice Questions as classified in NCERT Exemplar

Ans:  Option (iii) 1:3

The chlorine is a mixture of two isotopes with atomic masses 37U and 35U and its atomic mass is 35.5U. The atomic mass depicts that % composition of Cl-35 is much higher than that of Cl-37 and they are present in the ratio 1:3

This is a Short Answer Type Questions as classified in NCERT Exemplar

Molar mass of NaOH = 40 g/ mole

Molar mass of water =18 g / mole

Mass of NaOH= 4 g

Number of moles of 4 g NaOH = $\frac{4\mathrm{}\mathrm{g}}{40\mathrm{}\mathrm{g}\mathrm{}}$ = 0.1 mol

Number of moles of H₂O= $\frac{36\mathrm{}\mathrm{g}}{18\mathrm{}\mathrm{g}\mathrm{}}$ =2 mol

Mole fraction of water

$\frac{26\mathrm{}\mathrm{g}}{\mathrm{N}\mathrm{u}\mathrm{m}\mathrm{b}\mathrm{e}\mathrm{r}\mathrm{}\mathrm{o}\mathrm{f}\mathrm{}\mathrm{m}\mathrm{o}\mathrm{l}\mathrm{e}\mathrm{s}\mathrm{}\mathrm{o}\mathrm{f}\mathrm{}\mathrm{N}\mathrm{a}\mathrm{O}\mathrm{H}+\mathrm{}\mathrm{N}\mathrm{u}\mathrm{m}\mathrm{b}\mathrm{e}\mathrm{r}\mathrm{}\mathrm{o}\mathrm{f}\mathrm{}\mathrm{m}\mathrm{o}\mathrm{l}\mathrm{e}\mathrm{s}\mathrm{}\mathrm{o}\mathrm{f}\mathrm{}{\mathrm{H}}_2\mathrm{O}}$

Mole fraction of NaOH = $\frac{2\mathrm{}\mathrm{g}}{0.1\mathrm{}+\mathrm{}2\mathrm{}\mathrm{g}\mathrm{}}$  = $\frac{2\mathrm{}\mathrm{g}}{2.1\mathrm{}\mathrm{g}\mathrm{}}$  = 0.95

Number of moles of= $\frac{2\mathrm{}\mathrm{g}}{0.1\mathrm{}\mathrm{g}\mathrm{}}$  = $\frac{0.1\mathrm{}\mathrm{g}}{2.1\mathrm{}\mathrm{g}\mathrm{}}$ = 0.047

Number of moles of NaOH

Mass of solution = Mass of solute + Mass of solvent

Mass of NaOH + Mass of water 4 g + 36 g = 40 g

Specific gravity of solution =1 g / ml

1 litre =1000 ml volume of solution = 40ml

40ml = 0.04 litre

Molarity = $\frac{\mathrm{n}\mathrm{u}\mathrm{m}\mathrm{b}\mathrm{e}\mathrm{r}\mathrm{}\mathrm{o}\mathrm{f}\mathrm{}\mathrm{m}\mathrm{o}\mathrm{l}\mathrm{e}\mathrm{s}\mathrm{}\mathrm{o}\mathrm{f}\mathrm{}\mathrm{s}\mathrm{o}\mathrm{l}\mathrm{u}\mathrm{t}\mathrm{e}}{\mathrm{V}\mathrm{o}\mathrm{l}\mathrm{u}\mathrm{m}\mathrm{e}\mathrm{}\mathrm{i}\mathrm{n}\mathrm{}\mathrm{l}\mathrm{i}\mathrm{t}\mathrm{r}\mathrm{e}}$ = $\frac{0.1\mathrm{}\mathrm{m}\mathrm{o}\mathrm{l}}{0.04\mathrm{}\mathrm{l}\mathrm{i}\mathrm{t}\mathrm{r}\mathrm{e}\mathrm{}}$ = 2.5M

This is a Multiple Choice Questions as classified in NCERT Exemplar

Ans: Option (i)

 “l” which is known as Azimuthal quantum number or orbital angular momentum or subsidiary quantum number depicts the three dimensional shape of the orbital.

This is a Short Answer Type Questions as classified in NCERT Exemplar

Molality is the number of moles of substance (also known as the solute) found in a given mass of solvent (in Kg ) in which it is dissolved. Molality is calculated by using the formula.

Molality = $\frac{\mathrm{N}\mathrm{u}\mathrm{m}\mathrm{b}\mathrm{e}\mathrm{r}\mathrm{}\mathrm{o}\mathrm{f}\mathrm{}\mathrm{m}\mathrm{o}\mathrm{l}\mathrm{e}\mathrm{s}\mathrm{}\mathrm{o}\mathrm{f}\mathrm{}\mathrm{s}\mathrm{o}\mathrm{l}\mathrm{u}\mathrm{t}\mathrm{e}\mathrm{}}{\mathrm{S}\mathrm{o}\mathrm{l}\mathrm{v}\mathrm{e}\mathrm{n}\mathrm{t}\mathrm{}\mathrm{i}\mathrm{n}\mathrm{}\mathrm{k}\mathrm{g}\mathrm{}}$

So, temperature has no effect on the molality of the solution because molality is expressed in mass.

This is a Multiple Choice Questions as classified in NCERT Exemplar

Ans:  option (iii) 9

The total number of orbitals is given by n2, where n is the principal quantum number or the principal shell.

Thus for the third shell number of orbitals is 32 i.e. 9