TS EAMCET 2019 :: Chemistry :: General questions

• Chemistry - General questions

How many of the following compounds show ferrimagnetism?

$Fe_{3}O_{4};MgFe_{2}O_{4};NiFe_{2}O_{4};MnO;CrO_{2}$

Answer:

Explanation:

 In ferrimagnetic substances, the magnetic moment of the domains are aligned in parallel and antiparallel directions in unequal number. The net magnetic moment is small. Thus, these are weakly attracted by magnetic field than ferromagnetic substances and these also lose ferrimagnetism on heating and become paramagnetic. e.g. $Fe_{3}O_{4}$ and ferrite like $ZnFe_{2}O_{4}, MgFe_{2}O_{4}$  and $Ni Fe_{2}O_{4}$ etc

Among the given options , we have 3 compounds (i.e, $Fe_{3}O_{4},MgFe_{2}O_{4}$  and $NiFe_{2}O_{4}$)  that show ferrimagnetism.

Hence, option (c)  is the correct answer

Which  one of the following methods can be used to find out the percentage composition of halogen present in an organic compound ?

Answer:

Explanation:

(a) Kjeldahl method  can be used for estimation of nitrogen in an organic sample

(b)  Dumas method can be used for estimation of nitrogen  in an organic sample

(c) Lassaigne method can be used for estimation of N, S, P  and halogens in an organic sample

(d) Carius method    can be used to find out the percentage composition of halogen present in an organic compound using Carius tube

$\triangle H^{0}_{f}$ values (in $ kJ mol ^{1}$) for graphite , diamond and $C_{60}$  are respectively

Answer:

Explanation:

$\because$    Graphite is the most stable  state of carbon and its  $\triangle H^{0}_{f}$ is considered as zero ( $\because$  has more van der Waals'  force )  also $\triangle H^{0}_{f}$ for $C_{60}$ > $\triangle H^{0}_{f}$ for diamond

$\triangle H^{0}_{f}$ values of graphite  , diamond and $C_{60}$ are =0,  1.9 and 38.1 k J mol^-1 and $\triangle H^{0}_{f}$ values are in order:

Diamond < Fullerene < Graphite

Hence , option (a) is the correct answer.

Which of the following products are formed on hydrolysis of $NaO_{2}$?

(A)  NaOH   (B) $H_{2}O_{2}$   (C)   $O_{2}$   (D)  $H_{2}O$

Answer:

Explanation:

On hydrolysis  of NaO₂  ,( a superoxide  of sodium)  , it gives O₂, H₂O₂ and NaOH  as products.

i.e,

 $2NaO_{2}+2H_{2}O\rightarrow 2NaOH+O_{2}+H_{2}O_{2}$

 Hence , option (d)  is the correct answer

For the reaction ,

$0.5 C(s)+0.5 CO_{2}(g)\rightleftharpoons CO(g)$

the equilibrium pressure is 12 atm . If CO₂ conversion is 50%  the value  of K_p, in atm is 

Answer:

Explanation:

 For the reaction,

$0.5 C(s)+0.5 CO_{2}(g)\rightleftharpoons CO(g)$

 $0.5 CO_{2}(g)$ can give CO(g) .

If 50% conversion  of $CO_{2}(g)$ takes place.

We have concentration  of $CO_{2}(g)$ = [0.25]

$\because$  K_p  is calculated only for gaseous  items,

thus

$K_{p}= \frac{[product]_{(g)}}{[Reactant]_{g}}= \frac{[1]}{[0.25]}=4$

 Hence, option (a) is the correct answer.

• Chemistry - General questions