JEE 2017 :: Advanced 2017 :: Chemistry 2017

• Advanced 2017 - Physics 2017
• Advanced 2017 - Chemistry 2017
• Advanced 2017 - Mathematics 2017

The conductance  of a 0.0015 M aqueous solution of a weak monobasic acid was determined by using a conductivity cell consisting of platinised pt electrodes.  The distance between the electrodes  is 120 cm with an area of cross section of 1 cm². The conductance of this solution was found to be 5× 10^-7 S. The pH of the solution is 4. The value of limiting molar conductivity ( $\wedge^{0}_{m}$) of this weak monobasic acid in aqueous solution is Z× 10² S cm^-1 mol^-1. The value of Z is

Answer:

Explanation:

 pH = C $\alpha =10^{-4}$

 $\Rightarrow$   $\alpha  =\frac{10^{-4}}{.0015}$

 Also, onductance (G)=  $K(\frac{A}{I})$

 $\Rightarrow$   $K=G(\frac{I}{A})=5 \times 10^{-7}\times \frac{120}{1}=6\times 10^{-5}$

  $\Rightarrow$   $\wedge^{c}=\frac{k\times 1000}{C}$

  =  $\frac{6 \times 10^{-5}\times 1000}{.0015}$

  $\Rightarrow$   $\wedge^{\infty}=\frac{\wedge^{c}}{\alpha}=\frac{6\times10^{-5}\times1000}{.0015}\times\frac{0.0015}{10^{-4}}$

        =600=6 x10²  S cm^-1 mol^-1

A crystalline solid of a pure substance has a face-centered cubic structure with a cell edge of 400 pm. If the density of the substance in the crystal is 8 g cm^-3 , then the number of atoms present in 256 g of the crystal is N × 10²⁴.  The value  of N is 

Answer:

Explanation:

Density (ρ )=  $8=\frac{4\times M}{N_{A}(4\times 10^{-8}cm)^{3}}$

                         M= 128 × 10^-24 N_A

$\Rightarrow$     No of atoms=  $\frac{256}{M}\times N_{A}$

    =   $\frac{256}{128\times 10^{-24}N_{A}}\times N_{A}$

   =2 × 10²⁴

The color of the X₂ molecules of group 17 elements changes gradually from yellow to violet down the group. This is due to

Answer:

Explanation:

Color of halogen arises due to the transition from HOMO to LUMO   in the visible regions. On moving down a group, the difference in energy between HOMO  and LUMO decreases electronic transition occurs more easily and color intensity increases.

The correct statment(s) about the oxoacids, HClO₄ and HClO, is(are)

Answer:

Explanation:

(a) $ClO_{4}^{-}$  is more stable than ClO^-

(b) In correct: Cl₂ +H₂O → HCl +HOCl

(c)     

(d) HClO₄  is stronger acid than H₂O

An ideal gas is expanded form (p₁, V₁, T₁) to ( p₂, V₂, T₂) under different conditions. The correct statement(s) among the following is (are)

Answer:

Explanation:

Irreversible Compression

Reversible compression

Maximum work is done on the system when compression occurs irreversible and minimum work is done is reversible compression

(b)

AB is isothermal and AC  is the adiabatic path. Work was done in an area under the curve. Hence, less work is obtained in adiabatic process than in isothermal process.

  (c)   It is incorrect. In adiabatic expansion cooling is observed , hence 

  $\triangle U=nC_{v}\triangle T<0$

(d)   q=0( adibatic) W=0(Free expansion)

Hence   Δ U=0 , Δ T=0( isothermal)

• Advanced 2017 - Physics 2017
• Advanced 2017 - Chemistry 2017
• Advanced 2017 - Mathematics 2017