Which one of the sample has largest mass?

A. 1 mol of Na2S B. 3.0 x #10^24# molecule of O2 C. 8.8 x 10 g of NaCl D. 1.2 x #10^24# atoms of KThe answer is B. 3.0 x #10^24# molecule of O2, why?

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A. 1 mol of Na2S B. 3.0 x #10^24# molecule of O2 C. 8.8 x 10 g of NaCl D. 1.2 x #10^24# atoms of KThe answer is B. 3.0 x #10^24# molecule of O2, why?
Answer (Detailed Solution Below)
Which molecule has the largest mass?
Which sample has the largest molar mass?
How do you find the mass of a sample?
Which one of the samples contains the most atoms?

To calculate the mass of 1 mol of #"Na"_2"S"# we need just to multiply it by it's molar mass: 78,0452 g/mol. Therefore the result will be 78,0452 g.

To calculate the mass of #"O"_2#, we first need to divide the result by the Avogadro constant.

#3.0 × 10^24color(white)(l) "molecules O"_2 × "1 mol O"_2/(6.022 × 10^23color(white)(l) "molecules O"_2) = "4.98 mol O"_2#

This gives us the moles of #"O"_2 #.

Then we multiply by the molar mass.

#"4.98 mol O"_2 × "32.00 g O"_2/"1 mol O"_2 = "160 g O"_2#

For C we only have 88 g.

And for D the molar mass of #"K"# is 39,0983 g/mol.

This means

#1.2 × 10^24color(white)(l) "atoms" × "1 mol"/(6.022 × 10^23color(white)(l) "atoms") × "39.10 g"/"1 mol" = "80 g"#

This question was previously asked in

HTET TGT Mathematics and Science 2012 - 2013 Official Paper

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16.0 grams of O2
0.8 mole of O2
6.02 × 1023 molecules of O2
20.4 litre of O2 at STP

Answer (Detailed Solution Below)

Option 3 : 6.02 × 1023 molecules of O2

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The correct answer is 6.02 × 1023 molecules of O2.

Key Points

Concept:

6.02 x 1023 molecules of O2 has more mass.

Calculation:-

16 grams of O2 -

No. of moles = given mass/molar mass = 16 gm / 32 gm = 1/2, Mass of one mole of O2= 2 x atomic mass of O2 = 32 gm, Mass of 16gm of O2 = 1/2 x 32 gm = 16 gm

0.8 mole of O2 -

No of moles of O2 = 0.8, Mass of one mole of O2= 2 x atomic mass of O2 = 32 gm, Mass of 0.8 moles of O2 = 0.8 x 32 gm = 25.6 gm

6.02 x 1023 molecules of O2 -

No. of moles = given no of particles / Avogadro no = 6.02 x 1023 / 6.02 x 1023 = 1,Mass of 6.02 x 1023 molecules of O2 = 1 x 32 gm = 32 gm

20.4 liter of O2 at STP -

No. of moles = given Volume / 22.4 Liter = 20.4 / 22.4 = 0.91, Mass of one mole of O2= 2 x atomic mass of O2 = 32 gm, Mass of 20.4 liter of O2 in STP = 0.911 x 32 gm = 29.14 gm

Additional Information

In the SI system, mole (symbol, mol) was introduced as the seventh base quantity for the amount of a substance.
The mole, symbol mol, is the SI unit of the amount of substance. One mole contains exactly 6.02214076× 1023 elementary entities.
This number is the fixed numerical value of the Avogadro constant, NA, when expressed in the unit mol–1 and is called the Avogadro number.
The amount of substance, symbol n, of a system is a measure of the number of specified elementary entities.
An elementary entity may be an atom, a molecule, an ion, an electron, any other particle or specified group of particles.
It may be emphasized that the mole of a substance always contains the same number of entities, no matter what the substance may be. In order to determine this number precisely, the mass of a carbon–12 atom was determined by a mass spectrometer and found to be equal to 1.992648 × 1023 g. Knowing that one mole of carbon weighs 12 g, the number of atoms in it is equal to = 6 0221367 x 1023 . atoms /mol 2

Last updated on Sep 22, 2022

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How do you find the mass of a sample?

The molar mass is the mass of one mole of a sample. To find the molar mass, add the atomic masses (atomic weights) of all of the atoms in the molecule. Find the atomic mass for each element by using the mass given in the Periodic Table or table of atomic weights.