Question

(5 marks Answer)
The atomic mass of an element is in fraction . What does this mean ??

(3 marks Answer)
Find out the mass of
$\sf Co_2$
in reaction
$\sf {CaCo_3}^{heat} \longrightarrow CaO + Co_2$
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Answer 1

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• The atomic mass of an element is in fraction when there an mixture of isotopes with different masses in it, this is why sometimes atomic mass of an element are in fraction form.

${\sf{\underline{\boxed{\pink{\sf{FORMULA: }}}}}}$

• $\sf{Average \: mass = \dfrac{Total \: mass \: of \: Atoms}{Total \: number \: of \: atoms}}$

Using this formula, we can calculate the atomic mass:-

• Let us frame a simple question by our own and find the average mass.

${\sf{\underline{\boxed{\green{\sf{Question: }}}}}}$

Given:

• Let us assume that, the 2 boxes of salt has 5g mass and 2 boxes of sugar has 7g mass.

Find:

• Find the average mass of salt and sugar.

Calculations:

• We know that:-

1. Salt = 5g
2. Sugar = 7g.

⇢ $\sf{Mass \: of \: salt + Mass \: of \: sugar}$

⇢ $\sf{5g + 6g = 11g}$

So,

⇢ $\sf{Average \: mass = 11 gram \: (4 \: boxes)}$

⇢ $\sf{Average \: mass = 2.75g}$

HENCE PROVED!!

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• 1 mole of CaCO3 begets 1 more of CO2.

• So maybe this would be work.

= 44.01/100.0869

= 0.439717885

Answer 2

Answer 1

The atomic mass of an element is in fraction, this means that that mass of one atom of an element is divided the one atomic mass unit that is mass equal to 1/12th of mass of one carbon - 12(C) atom.

Actually atomic mass in fraction means :-

a) when the element has different isotopes, then the atomic mass of each isotope is presented in the form of percentage. This percentage is further on expressed as fraction.

b) Also, while finding the atomic mass of an atom of any element, we divide the mass of an element by the mass equal to one - twelfth of mass of one carbon - 12 atom. This is also represented in the form of fraction.

Answer 2

Given

$\bf CaCo_3 \: (s) \longrightarrow CO_2 \: (g) + Ca(OH)_2 \: (s)$

This, can be written as

$\bf 1CaCo_3 \: (s) \longrightarrow 1 CO_2 \: (g) + Ca(OH)_2 \: (s)$

From the Balanced Equation above, we get One Mole of Ca(Co)₃ on heating gives 1 mole of CO₂ and 1 mole of Ca(OH)₂

This means that in this Reaction only 1 mole of CO₂ is formed.

Molecular Mass of CO₂

➱ 12 + 2(16)

➱ 12 + 32

➱ 44

Molar Mass of CO₂ = 44 g/mol

Hence, amount of CO₂ formed is 1 mole = 44 g

More to Know

1.) Atomic Mass Unit = a unit of mass used to express atomic and molecular weights, equal to one twelfth of the mass of an atom of carbon-12.

$\bf 1 \: amu = 1.6605610^ {(-24)}$

2.) Atomic mass of different elements = the mass of an atom of a chemical element expressed in atomic mass units. It is approximately equivalent to the number of protons and neutrons in the atom (the mass number) or to the average number allowing for the relative abundances of different isotopes.

For example

Mass of hydrogen atom = 1.673610-²⁴

In terms of amu, mass of hydrogen :-

$\bf 1.6736 ^ {(-24) } / 1.66056 ^ {(-24) } = 1.0080 = 1 amu$

3.) The average atomic mass of an element is the sum of the masses of its isotopes, each multiplied by its natural abundance (the decimal associated with percent of atoms of that element that are of a given isotope).

Average atomic mass = f1M1 + f2M2 +….....+ fnMn

Where, f corresponds to relative percentage of abundance and M corresponds to mass of that isotope.

The molecular mass (m) is the mass of a given molecule: it is measured in daltons (Da or u). Different molecules of the same compound may have different molecular masses because they contain different isotopes of an element.

The molar mass is the mass of a given chemical element or chemical compound (g) divided by the amount of substance (mol). The molar mass of a compound can be calculated by adding the standard atomic masses (in g/mol) of the constituent atoms.

For e.g. :-

Molecular mass of water (H2O) = 2(1) + 16 = 2 + 16 = 18 u

Molar mass of Water = 18 g/mol

Formula unit mass of a substance is the sum of the atomic masses of all the atoms present in the formula of a respective compound. The reason here why the formula unit is taken is that most of the ionic compounds do not have single entity.

Formula Mass of NaCl = 23.0u + 35.5 u = 58.5 u

The mole is the unit of measurement for amount of substance in the International System of Units. A mole of a substance or a mole of particles is defined as exactly 6.02214076×10²³ particles, which may be atoms, molecules, ions, or electrons. In short, for particles 1 mol = 6.02214076×10²³.

Avogadro's number is the number of units in one mole of a substance, or 6.02214076 × 1023. This number is also called the Avogadro constant. It is named after the 19th-century Italian physicist Amedeo Avogadro, who found that under the same temperature and pressure, two gases with the same volume have the same number of molecules. It was the French physicist Jean Perrin who in the early 20th century dubbed the amount of units in a mole as Avogadro's number.

According to the Ideal Gas Law of Avogadro,

Volume of any gas at S.T.P. = 22.4 L

Volume of any gas at N.T.P. = 22.7 L

Continuity of this Answer :-

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