Question

A mixture contains NaCl and unknown chloride MCl.(i) 1 g of this is dissolved in water. Excess of acidified AgNO₃ solution is added to it. 2.567 g of white ppt. is formed.(ii) 1 g of original mixture is heated to 300°C. Some vapours come out which are absorbed in acidified AgNO₃ solution, 1.341 g of white precipitate was obtained.Find the molecular weight of unknown chloride.
Please explain the solution. Please answer this. Urgent.​

Answer 1

Answer:

By statement given in (a)

Mass of NaCl=a g

Mass of MCl=b g

∴a+b=1

Also, Meq. of NaCl + Meq. of MCl = Meq. of AgNO

3

= Meq. of AgCl

=

143.5

2.567

×1000

Meq. of NaCl + Meq. of MCl =17.889

Now, as reported in statement (b),

Mixture is heated to 300 K. Since, NaCl is stable, the possibility seems for the decomposition of MCl and thus, after heating only MCl forms vapour which react with AgNO

3

.

Meq. of MCl = Meq. of AgNO

3

= Meq. of AgCl

=

143.5

1.341

×1000

Meq. of MCl =9.345

Meq. of NaCl=17.889−9.345=8.544

58.5

w

×1000=8.544

w

NaCl

=0.50 g

Meq. of MCl in mixture =9.345

M/1

w

×1000=9.345

M

1−0.50

×1000=9.345(∵a+b=1)

M=53.50

MCl may be NH

4

Cl.

So, answer is 53.

Answer 2

Explanation:

solve this problem, we can use the identities:

sinA+sinB=2sinA+B2cosA−B2,

cosA+cosB=2cosA+B2cosA−B2,

and

sin2ϕ=2sinϕcosϕ.

Going back to the question,

LHS=sin2x+sin4x+sin6x=2sin3xcosx+sin6x=2sin3xcosx+2sin3xcos3x=2sin3x(cosx+cos3x)=2sin3x×2cos2xcosx=4cosxcos2xsin3x=RHS.

Hence, proved.