Suppose two elements X and Y combine to form two compounds XY2 and X2Y3 when 0-05 mole of XY2 weights 5 g while 3-011- 1023 molecules of X2Y3 weighs 85 g- The atomic masses of X and Y are respectively-

The correct option is C 40, 30 MassMolar mass = Mole 5gmw = 0.05 ⇒ mw = 100 x+2y = 100 ...(i) No. of molecules6 × 10^23 = massmw eq ...

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Standard X

Chemistry

Mole Concept

Suppose two e...

Question

Suppose two elements $X$ and $Y$ combine to form two compounds $X Y_{2}$ and $X_{2} Y_{3}$ when $0.05$ mole of $X Y_{2}$ weights $5$ g while $3.011 \times 10^{23}$ molecules of $X_{2} Y_{3}$ weighs $85$ g. The atomic masses of $X$ and $Y$ are respectively:

20, 30

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30, 40

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40, 30

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80, 60

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Solution

The correct option is C $40, 30$
$\frac{M a s s}{M o l a r m a s s} = M o l e$

$\frac{5 g}{m w} = 0.05 \Rightarrow m w = 100$

$x + 2 y = 100 . . . (i)$

$\frac{N o . o f m o l e c u l e s}{6 \times 10^{23}} = \frac{m a s s}{m w}$

eq $(1) \times 2$

$\frac{3.011 \times 10^{23}}{6.023 \times 10^{23}} = \frac{85}{m w} \Rightarrow m w = 170$

$2 x + 3 y = 170 . . . . (i i)$

On solving equation (i) and (ii), we get-
$2 x + 4 y = 200$
$2 x + 3 y = 170$

$y = 30$

$2 \times x + 3 \times 30 = 170$

$2 x = 170 - 90$

$2 x = 80$

$x = 40$

So, the correct option is $C$

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Suppose two elements X and Y combine to form two compounds XY2 and X2Y3 when 0.05 mole of XY2 weights 5 g while 3.011×1023 molecules of X2Y3 weighs 85 g. The atomic masses of X and Y are respectively:

The correct option is C 40,30MassMolarmass=Mole5gmw=0.05⇒mw=100x+2y=100...(i)No.ofmolecules6×1023=massmweq(1)×23.011×10236.023×1023=85mw⇒mw=1702x+3y=170....(ii)On solving equation (i) and (ii), we get- 2x+4y=2002x+3y=170y=302×x+3×30=1702x=170−902x=80x=40So, the correct option is C

Suppose two elements $X$ and $Y$ combine to form two compounds $X Y_{2}$ and $X_{2} Y_{3}$ when $0.05$ mole of $X Y_{2}$ weights $5$ g while $3.011 \times 10^{23}$ molecules of $X_{2} Y_{3}$ weighs $85$ g. The atomic masses of $X$ and $Y$ are respectively: