TS EAMCET 2019 :: Chemistry :: General questions

• Chemistry - General questions

 A polymer contain 50 molecules  with molecular  mass 5000 ,100 molecules with molecular mass 10000 and 50 molecules  with molecular  mass 15,000 . Calculate number average molecular mass ?

Answer:

Explanation:

 $\because$   Number average molecular mass   $(M\overline{n})$

 =$\frac{N_{1} M_{1}+N_{2} M_{2}+N_{3} M_{3}}{N_{1}+ N_{2}+N_{3}}$

 where, $N_{1},N_{2}  $   and $N_{3}$  are number of molecules and $M_{1} , M_{2} $ and $M_{3}$ are respectively  their molecular  masses.

 Given

      $N_{1}$ = 50   and $M_{1}$ = 5000

$N_{2}$ = 100   and $M_{2}$ = 10000

$N_{3}$ = 50   and $M_{3}$ = 15000

 Thus, 

 $M\overline{n}=\frac{N_{1} M_{1}+N_{2} M_{2}+N_{3} M_{3}}{N_{1}+ N_{2}+N_{3}}$

      =$M\overline{n}=\frac{(50 \times 5000) +(100\times 10000)+(50\times 15000)}{50+ 100+50}$

  = $\frac{(25,0000) +(1000000)+(750000)}{200}$

$M\overline{n}$=10,000

 Hence, option (c) is the correct answer

Which one of following complex has the  highest magnitude of crystal field splitting energy ($\triangle _{0}$)?

Answer:

Explanation:

 The crystal  field splitting , i.e, $\triangle _{0}$ , depends

upon the field produced by the ligand and charge on the metal ion.

 So, ligands can be arranged in a series  in the order of increasing field strength  . This  series known  as spectrochemical series

eg.  I^Θ<Br^Θ  <SCN^Θ <Cl^Θ  <F^Θ <OH^Θ < C₂O₄^2-

 $<H_{2}O $ < NCS^Θ < EDTA ^4- <$NH_{3}$  < en < CN^Θ    <CO $\because$

Among the given options , ligand ($NH_{3}$) has highest magnetic field therefore , it has maximum value for  $\triangle _{0}$. 

Hence option (b) is the correct answer

Statement   (A)  Sulphur vapour is paramagnetic

Statement (B) Reaction of dil.HCl with finely divided  iron forms $FeCl_{3}$ and $H_{2}$ gas

 The correct answer is 

Answer:

Explanation:

Statement (A)  Sulphur vapour is  paramagnetic is correct statement as sulphur vapour has formula $S_{2}$ , i.e, similar to $O_{2}$  and $O_{2}$ has two unpaired  electrons in its anti-bonding molecular orbitals

Statement (B)   Reaction of HCl (dil.) with finely divided iron forms $FeCl_{3}$ and $H_{2}$ gas  isa wrong  statement as the  whole reaction in as follows :

$Fe+2HCl(dil.)\rightarrow FeCl_{2}+H_{2}(g)$

 The $H_{2}$ (g)   produced will prevent the formation  of $Fe^{3+}$ (i.e, $FeCl_{3}$)

Hence, option (a)   is the correct answer

 Which one of the following is used as an eye lotion?

Answer:

Explanation:

Silver sols can be used as wye-lotion because it can heal eye infections.

Hence , option(b) is the correct answer

 The freezing point  of solution containing  10 mL  of non-volatile and non-electrolyte liquid " A" in 500 g of water is $-0.413^{0} C$. If $K_{f}$ of water is 1.86 K kg $mol^{-1}$ and the molecular weight of A=60 g $mol^{-1}$, what is the density  of the  solution in g $mL^{-1}$ ?

 (Assume  $\triangle  _{mix}$v=0)

Answer:

Explanation:

Given,

 Volume of solute =10 mL

 $\triangle T_{f}=0-(-0.413)=0.413^{0}C$

 w(solvent) =500g

$K_{f}(water)$=1.86 K kg $mol ^{-1}$ ($=w_{A}$)

Molecular weight of (A) or $M_{B}$  = 60g

 Let mass of solute (A) = w_B

 $\therefore$    $\triangle T_{f}=K_{f}\times\frac{w_{B}}{M_{B}}\times\frac{1000}{w_{A}}$

        $0.413=1.86\times\frac{w_{B}}{60}\times\frac{1000}{500}$

 $\therefore$     $w_{B}=\frac{0.413 \times60\times500}{1.86\times 1000}$

 Mass of solute =6.66 g

 Also, $\because$   Density (d) of solution  = Total mass/ Total volume

 = $\frac{6.66+500}{500+10}= \frac{506.66}{510}$= 0.993 (g $mL^{-1}$)

 Density (d) of solution =0.993 g m L^-1

 Hence , option (d)  is the correct answer 

• Chemistry - General questions