Question

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Answer 1

$\displaystyle\large\underline{\sf\red{Given}}$

• ✭ Mass of 112 ml of a certain gas is 22 g at STP

$\displaystyle\large\underline{\sf\blue{To \ Find}}$

• ◈ Number of molecules

• ◈ Molar mass?

$\displaystyle\large\underline{\sf\gray{Solution}}$

• We should convert the volume from 112 ml to l,

• ›› 1 ml = 1000 l

• ›› 112 ml = 112/1000

• ›› Volume = 0.112 l

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$\underline{\bigstar\:\textsf{According to the given Question :}}$

We know that,

$\displaystyle\underline{\boxed{\sf Number \ of \ moles = \dfrac{Volume}{Volume \ at \ STP}}}$

Volume = 0.112 l

Volume of gas at STP = 22.4

Substituting the values,

➝ $\displaystyle\sf Number \ of \ moles = \dfrac{Volume}{Volume \ at \ STP}$

➝ $\displaystyle\sf \dfrac{0.112}{22.4}$

➝ $\displaystyle\sf \purple{Number \ of \ moles = 0.005 \ mol}$

So then the number of molecules will be,

➳ $\displaystyle\sf 0.005\times 6.0221\times 10^{24}$

➳ $\displaystyle\sf \orange{Number \ of \ molecules = 30.11\times 10^{21}}$

So then the molar mass will be given by,

$\displaystyle\underline{\boxed{\sf Number \ of \ moles = \dfrac{Given \ Mass}{Molar \ Mass}}}$

Substituting the values,

»» $\displaystyle\sf 0.005 = \dfrac{0.22}{Molar \ Mass}$

»» $\displaystyle\sf Molar \ Mass = \dfrac{0.22}{0.005}$

»» $\displaystyle\sf \pink{Molar \ Mass = 44 \ g}$

$\displaystyle\therefore\:\underline{\sf Molar \ mass \ is \ 44g \ \& \ Nmbr \ of \ molecules \ is \ 30.11\times 10^{21}}$

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Answer 2

We should know that at STP,

Pressure (P)is 10^5pascal and Temperature(T) is 273kelvin and Universal gas constant(R) is 8.31J/K

And we have take volume (V)in m³ so use....n=PV/RT.