Question

Calculate the number of moles of each substance in
following
(b) 250mg of carbon (c) 15g of sodium chloride
Calculate the mass in arams of each of the following samples:
masses:
(a) 2.4 g of He
(d) 40g of sulphur (e) 1.5kg of Mgo​

Answer 1

$\huge\bigstar\boxed{\pink{\sf solution:-}}\bigstar$

we know that to calculate moles when mass of a substance is given is calculated by:

$\boxed {\blue {\tt moles=\dfrac {given \:mass }{molecular \:mass}}}$

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given mass :- 250mg of carbon

atomic mass of carbon = 12g

$\tt no. \:of\: moles =\dfrac {250×10^{-3}}{12}$

$\boxed {\tt\implies 0.02 moles }$

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given mass :- 15g of sodium chloride

molecular mass = 23 + 35.5

= 58.5g

$\tt no. \: of \: moles = \dfrac {15}{58.5}$

$\boxed{\tt\implies moles \approx 0.25 }$

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given mass = 2.4g of helium

atomic mass = 4g

$\tt moles = \dfrac {2.4}{4}$

$\tt moles = 0.6$

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given mass = 1.5kg = 1500g

atomic mass = 24+16 = 40g

$\tt moles = \dfrac{1500 }{40}$

$\tt moles = 37.5$

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$\huge\bigstar\boxed{\pink{\tt extra\: information}}}\bigstar$

to convert moles to mass we multiply the given mass by atomic number of the element.

to calculate the number of atoms or ions, we multiply using the avagadro number.

hope this helps!

Answer 2

Answer:

250 mg of carban calculate moles