VITEEE 2014 :: Chemistry :: General questions

• Chemistry - General questions

The standard molar heat of formnation of ethane , $CO_{2}$ and water (l) are respectively -21.1 ,-94.1 and -68.3 kcal . The standard molar heat of combustion of ethane will be 

Answer:

Explanation:

Given, 

(a)  $2C+3H_{2} \rightarrow  C_{2}H_{6}; \triangle H=-21.1 kcal$

(b)   $C+O_{2} \rightarrow  CO_{2}; \triangle H=-94.1kcal$

(c)   $H_{2}+\frac{1}{2}O_{2} \rightarrow H_{2}O; \triangle H= -68.3 kcal$

Now, eqs, $2 \times (b) +3\times (c)-(a)$

$C_{2}H_{6}+\frac{3}{2}O_{2} \rightarrow 2CO_{2}+3H_{2}O$

Heat  of combustion  of ethane  $\triangle x=2(-94.1)$

+3(-68.3)-(-21.1)

=$(-188.2)+(-204.9)-21.1$

=$-372 kcal$

An f-shell containing 6 unpaired electrons are exchange 

Answer:

Explanation:

 5+4+3+2+1=15

 $\therefore$ equation of normal  of x= 0 and y=1 is y-1=-1(x-0)

 $\Rightarrow$  $y-1=-x \Rightarrow x+y=1$

19.85mL of 0.01NaOH reacts with 20mL  of  HCl solution for complete neutralisation. the molarity of HCl solution is 

Answer:

Explanation:

Molarity of base= $\frac{normality}{acidity}=\frac{0.1}{1}=0.1$

 $M_{1}V_{1}=M_{2}V_{2}$

$0.1 \times 19.85=M_{2} \times20$

$M_{2}=0.09925  \approx 0.099$

The rate constant for forward reaction and backward reaction of hydrolysics of ester are $1.1 \times 10^{-2}$ and $1.5 \times 10^{-3}$ per minute respectively . Equilibrium constant for the reaction is 

$CH_{3}COOC_{2}H_{5} + H_{2}O \rightleftharpoons CH_{3}COOH+C_{2}H_{5}OH$

Answer:

Explanation:

given $k_{f}=1.1 \times 10^{-2} , k_{b}=1.5 \times 10^{-3}$

$k_{c}=\frac{k_{f}}{k_{b}}=\frac{1.1 \times 10^{-2}}{1.5 \times 10^{-3}}=7.33$

Which of the following hydrogen bonds are strongest in the vapour phase?

Answer:

Explanation:

A compound having maximum electronegative element will form a strong hydrogen bond. F is the most negative  element among halogens hence forming the strongest hydrogen bond 

• Chemistry - General questions