MHT CET 2019 :: Chemistry :: General questions

• Chemistry - General questions

 The activation energy of a reaction is zero, Its rate constant at 280 K is 1.6 x 10^-6 s^-1 , the rate constant at 300K is 

Answer:

Explanation:

Key Idea: Arrhenius  equation is given as:

 $\log\frac{k_{2}}{k_{1}}=\frac{E_{a}}{2.303 R}\left[\frac{1}{T_{1}}-\frac{1}{T_{2}}\right]$

 Given,

 Activation  energy  of a reaction , E_A =0

 Rate constant  , k₁ =1.6 x 10^-6 s^-1

 Temperature  , T₁ =280 K, T₂ =300K

 According to Arrhenius  equation

$\log\frac{k_{2}}{1.6\times 10^{-6}}=\frac{0}{2.303 R}\left[\frac{1}{280}-\frac{1}{300}\right]$

$\log\frac{k_{2}}{1.6\times 10^{-6}}=0$

$\frac{k_{2}}{1.6\times 10^{-6}}=antilog 0$

 $\frac{k_{2}}{1.6\times 10^{-6}}=1$

$\therefore$     $k_{2}=1.6\times 10^{-6}s^{-1}$

 Which of the following elements does not form amide when reacted with ammonia?

Answer:

Explanation:

Lithium doesn't form amide when reacted with ammonia. It forms tetraamminelithium , Li(NH₃)₄.

 The equation for the reaction is as follows:

$Li+4NH_{3}\rightarrow  [Li(NH_{3})_{4}]$

                            Tetraaminelithium

Which among the following is a neutral complex ? 

Answer:

Explanation:

 A neutral complex is a complexion that has no charge on it. Among the given options 

[Pt(NH_{3})_{2}]Cl_{2}]$ is a  neutral  complex. The type of complexes in other options are as follows.

 (a)  $[Fe(H_{2}O)_{6}]Cl_{3}$- cationic complexes

(b)  $[Ni(NH_{3})_{6}]Cl_{6}$  - cationic complexes

(d)  $K[Ag_{}(CN)_{2}]$  - anionic complexes

 How many total constituent particles are present in a simple cubic unit cell?

Answer:

Explanation:

 A simple cubic lattice has only eight atoms on the corners. As the contribution  by each = $\frac{1}{8}$

 Therefore , a number of constituent  particles (atoms)  present in a unit cell = $\frac{1}{8}\times 8=1$

 The number of $\sigma$  and $\pi$- bonds in 2-formylbenzoic acid are  respectively

Answer:

Explanation:

 Structure of  2-formyl benoic acid is 

 Thus, it has 17 $\sigma$ and 5 $\pi$ bonds.

• Chemistry - General questions