How To Find Number Of Atoms Given Grams

Science > Chemistry > Molecule and Molecular Mass > Calculation of Number of Moles, Atoms, and Molecules

In this article, nosotros shall study the calculation of number of moles, number of atoms, and molecules in a given moles.

Schematic Diagram for Mole Calculations:

Where, g = Given mass, M = Molar mass

v = Given volume, 5 = Molar volume = 22.four dm ³

n = Number of moles = grand/G

Number of atoms  = Number of molecules  × Atomicity

Conversions:

From	To	Factor
kg	g	× 10iii
mg	thou	× 10-three
μg	chiliad	× ten-6
metric ton	kg	× 10three
metric ton	g	× 106
cm iii	dm iii	× ten-iii
grand 3	dm 3	× ten3
litre	dm 3	× i

To Calculate Number of Moles:

Summate the number of moles of following.

 7.85 k of Fe (at. mass 56)

Given mass of Fe = seven.85 g

Atomic number 26 is a monoatomic molecule.

Hence molecular mass of Fe = Atomic mass of Fe = 56 chiliad

Number of moles of Fe = Given mass of Fe / Molecular mass of Fe

Number of moles of Iron  =  7.85 g / 56 g = 0.1402

Ans: Number of moles of Atomic number 26 = 0.1402

vii.9 mg of Ca (at. mass 40)

Given mass of Ca =seven.ix mg = seven.9 × 10^-3 g

Ca is a monoatomic molecule.

Hence molecular mass of Ca = Atomic mass of Ca = 40 g

Number of moles of Ca = Given mass of Ca / Molecular mass of Ca

Number of moles of Ca = 7.9 × 10^-3 thousand / twoscore thou = 1.975  × x^-4

Ans: Number of moles of Ca = ane.975  × 10^-iv

1.46 metric tons of Al (at. mass 27)

Given mass of Al = 1.46 metric tons = one.46 × 10^three kg

= 1.46 × ten^three × 10³yard = ane.46 × x⁶g

Al is a monoatomic molecule.

Hence molecular mass of Al = Atomic mass of Al = 27 thousand

Number of moles of Al = Given mass of Al / Molecular mass of Al

Number of moles of Al = ane.46 × 10⁶g / 27 chiliad = five.41  × 10^iv

Ans: Number of moles of Al = 5.41  × 10⁴

65.5 mg of C (at. mass 12)

Given mass of C = 65.5 mg = 65.five × x^-iii g

Al is a monoatomic molecule.

Hence molecular mass of C = Diminutive mass of C = 12 thou

Number of moles of C = Given mass of C/ Molecular mass of C

Number of moles of C = 65.v × 10^-three g / 12 chiliad = 5.46 × x^-3

Ans: Number of moles of C  = five.46 × 10^-3

To Calculate Number of Molecules in a Given mole:

Calculate the number of moles and number of molecules of following.

0.032 mg of methane

Molecular mass of marsh gas (CH₄) = 12 × 1 + ane × 4 = 12 + 4 = sixteen grand

Given mass of CH₄ = 0.032 mg = 0.032 × 10^-3 g = 3.two × x^-5 g

Number of moles of CH₄ =   north  =  Given mass of CH_four / Molecular mass of CH₄

n = 3.2 × 10^-5 g / 16 g = 2 × ten^-vi

At present, Number of molecules = No. of moles × Avogadro's number

Number of molecules = 2 × ten^-vi × half dozen.022 × 10²³

Number of molecules = 1.2044 × 10^eighteen

Ans: Number of moles of C  = five.46 × ten^-three and

Number of molecules = 1.2044 × x^xviii

6.iv × 10^-two kg of sulphur dioxide

Molecular mass of marsh gas (Then₂) = 32 × 1 + 16 × 2 = 32 + 32 = 64 thousand

Given mass of So₂ = 6.4 × 10^-ii kg = 6.four × 10^-2× 10^three g = 64 g

Number of moles of So₂ =   north  = Given mass of SO₂ / Molecular mass of And so₂

n = 64 yard / 64 g = i

Now, Number of molecules = No. of moles × Avogadro's number

Number of molecules = one × six.022 × 10²³

Number of molecules = half dozen.022 × 10²³

Ans: Number of moles of SO₂ = ane and Number of molecules =6.022 × ten²³

0.065 mg of water

Molecular mass of water (H₂O) = 1 × 2 + 16 × one = two + 16 = xviii g

Given mass of H₂O = 0.065 mg = 0.065 × 10^-3g = 6.5  × 10^-five g

Number of moles of H_twoO =   n  = Given mass of H₂O / Molecular mass of H₂O

n  = 6.5  × 10^-5 g / 18 g = 3.611  × 10^-6

At present, Number of molecules = No. of moles × Avogadro's number

Number of molecules = 3.611  × ten^-six × 6.022 × x²³

Number of molecules = ii.174 × 10¹⁸

Ans: Number of moles of H_iiO = iii.611  × x^-6 and Number of molecules = 2.174 × 10^eighteen

500 mg of carbon dioxide

Molecular mass of carbondioxide (CO₂) = 12 × 1 + xvi × 2 = 12 + 32 = 44 chiliad

Given mass of CO_two = 500 mg = 500 × 10^-3 g = 0.5 g

Number of moles of CO₂ =   due north  = Given mass of CO₂ / Molecular mass of CO_two

n  = 0.5 g / 44 m = one.136 × x^-2

Now, Number of molecules = No. of moles × Avogadro's number

Number of molecules = 1.136 × ten^-2 × half dozen.022 × 10²³

Number of molecules = half dozen.843 × 10²¹

Ans: Number of moles of CO₂ = i.136 × 10^-two and Number of molecules = 6.843 × 10²¹

Calculation of Number of Atoms in a Given Mole:

Calculate the number of moles, number of molecules and number of atoms of following.

1.1. × 10^-iv kg of carbon dioxide

Molecular mass of CO₂ =12 × 1 + 16 × 2 = 12 + 32 = 44 g

Given mass of CO₂ = 1.1. × 10^-4kg = 1.1. × ten^-4× ten³ g = 0.xi m

Number of moles of CO₂ = Given mass of CO₂ / Molecular mass of CO₂

Number of moles of CO_two = 0.11 chiliad / 44 g = 2.5 × 10^-iii

Now, Number of molecules = No. of moles × Avogadro's number

Number of molecules = two.5 × x^-3 × 6.022 × 10²³

Number of molecules of CO₂= 1.505 × ten²¹

Atomicity of CO₂ is 3

Hence Number of atoms in CO_ii = Number of molecules of CO_ii × Atomicity of CO_ii

Hence Number of atoms of CO₂ =  i.505 × 10²¹× three = 4.515 × 10²¹

Ans: Number of moles  = 2.5 × 10^-3 , Number of molecules = 1.505 × x²¹and Number of atoms =4.515 × ten²¹

4.25 × 10^-ii kg of ammonia

Molecular mass of NH_iii =14× 1 + i × 3 = fourteen + 3 = 17 g

Given mass of NH₃ = iv.25. × 10^-iikg = four.25. × 10^-2× 10³ g = 42.5  g

Number of moles of NH₃ = Given mass of NH₃ / Molecular mass of NH₃

Number of moles of NH₃ = 42.5 g / 17 one thousand = ii.5

Now, Number of molecules = No. of moles × Avogadro'southward number

Number of molecules = 2.five  × half-dozen.022 × 10²³

Number of molecules of NH₃= one.505 × 10²⁴

Atomicity of NH₃ is 4

Hence Number of atoms of NH_three = Number of molecules of NH₃ × Atomicity of NH_three

Hence Number of atoms in CO₂ =  one.505 × 10²⁴× 4 = vi.020 × 10²⁴

Ans: Number of moles  = 2.5, Number of molecules = 1.505 × 10²⁴and Number of atoms = 6.020 × 10²⁴

0.four thousand of helium gas.

Molecular mass of He = 4 g

Given mass of He = 0.4 g

Number of moles of He = Given mass of He / Molecular mass of He

Number of moles of He = 0.4 k / 4 thou = 0.1

Now, Number of molecules = No. of moles × Avogadro'southward number

Number of molecules = 0.1  × 6.022 × 10²³

Number of molecules of He= six.022 × x²²

Atomicity of He is 1

Hence Number of atoms of He = Number of molecules of He × Atomicity of He

Hence Number of atoms in He = 6.022 × x²²× i = half-dozen.022 × 10²²

Number of moles  = 0.ane, Number of molecules = 6.022 × 10²²and Number of atoms = 6.022 × 10²²

v.six cm³ of ammonia at STP.

Given volume of ammonia = five.six cm³ = 5.6 × 10^-three dm^three

ane mole of ammonia at STP occupies 22.iv dm³ by volume.

Number of moles of NH_iii = Given book of NH₃ / 22.4 dmⁱⁱⁱ

Number of moles of NH₃ = 5.6 × ten^-3 dmⁱⁱⁱ / 22.iv dm^three = ii.5 × 10^-4

At present, Number of molecules = No. of moles × Avogadro's number

Number of molecules = two.five × x^-four × half dozen.022 × x²³

Number of molecules of NH₃= 1.5055  × 10^twenty

Atomicity of NH_three is 4

Hence Number of atoms of NH_iii = Number of molecules of NH₃ × Atomicity of NH₃

Hence Number of atoms of NH₃ = i.5055  × 10^xx× four = 6.022 × 10²¹

Ans: Number of moles  = 2.5 × x^-4, Number of molecules = 1.5055  × 10²⁰and Number of atoms =half dozen.022 × 10²¹

5.6 dm³ of ammonia at STP.

Given volume of ammonia = 5.6  dm^three

ane mole of ammonia at STP occupies 22.4 dm³ past volume.

Number of moles of NH₃ = Given volume of NH₃ / 22.4 dm³

Number of moles of NH_three = 5.six  dm³ / 22.4 dmⁱⁱⁱ = 0.25

At present, Number of molecules = No. of moles × Avogadro's number

Number of molecules = 0.25 × 6.022 × 10²³

Number of molecules of NH_iii= 1.5055  × ten²³

Atomicity of NH₃ is 4

Hence Number of atoms of NH_iii = Number of molecules of NH₃ × Atomicity of NH₃

Hence Number of atoms of NH₃ = 1.5055  × 10²³× 4 = vi.022 × 10²³

Ans: Number of moles  = 0.25, Number of molecules = 1.5055  × ten²³and Number of atoms =vi.022 × x²³

seven.6 dm³ of hydrogen at STP.

Given volume of hydrogen = vii.vi dmⁱⁱⁱ

i mole of hydrogen at STP occupies 22.4 dm³ by volume.

Number of moles of H₂ = Given volume of H₂ / 22.4 dm³

Number of moles of H₂ = 7.half-dozen dm³ / 22.four dmⁱⁱⁱ =0.34

Now, Number of molecules = No. of moles × Avogadro'due south number

Number of molecules = 0.34 × 6.022 × 10²³

Number of molecules of H_ii = 2.047  × 10²³

Atomicity of H₂ is ii

Hence Number of atoms of H₂ = Number of molecules of H₂  × Atomicity of H₂

Hence Number of atoms of H_ii = 2.047  × 10²³× 2 = 4.094  × 10²³

Ans: Number of moles  = 0.34, Number of molecules = 2.047  × 10²³and Number of atoms = iv.094  × 10²³

250.9 dm^three of hydrogen at STP.

Given volume of hydrogen = 250.9 dm³

1 mole of hydrogen at STP occupies 22.4 dm³ by volume.

Number of moles of H_ii = Given volume of H₂ / 22.four dm³

Number of moles of H₂ = 250.9 dm³ / 22.4 dm^three = eleven.2

Now, Number of molecules = No. of moles × Avogadro'southward number

Number of molecules = 11.2 × half dozen.022 × 10²³

Number of molecules of H₂ = 6.745  × 10²⁴

Atomicity of H₂ is 2

Hence Number of atoms of H₂ = Number of molecules of H₂  × Atomicity of H₂

Hence Number of atoms of H₂ = 6.745  × 10²⁴× 2 = ane.349  × ten²⁵

Ans: Number of moles  = eleven.2, Number of molecules = 6.745  × 10²⁴and Number of atoms = i.349  × 10²⁵

Science > Chemistry > Molecule and Molecular Mass > Calculation of Number of Moles, Atoms, and Molecules

Source: https://thefactfactor.com/facts/pure_science/chemistry/physical-chemistry/calculation-of-number-of-moles-atoms-and-molecules/13028/

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