Question

how many atoms of calcium and oxygen are present in 25 g of calcium carbonate

Answer 1

1.5x10^23 calcium atoms

4.51×10^23 oxygen atoms.

Explanation:

The molecular weight of calcium carbonate is 100 g per mole. 

25 g of calcium carbonate corresponds to 0.25mole. 

1 molecule of calcium carbonate contains three oxygen atoms. 

Thus, 0.25 mole of calcium carbonate will contain 0.75 moles of oxygen atoms which is equal to 0.75×6.02×10^23=4.51×10^23 oxygen atoms.

similarly, 1 molecule of calcium carbonate contains 1 calcium atom.

therefore,no. of calcium atoms = 0.25*6.02*10^23

= 1.5x10^23 calcium atoms

:))

Answer 2

Answer:

In 25g of Calcium Carbonate,

• Number of Calcium atom is 1.5×6.02×10^23
• Number of Oxygen atom is 4.5×6.02×10^23

Explanation:

Mole is a number (6.02×10^23) which is also called as the Avagadro's number. In everyday life people use words such as a Dozen (12) or a a Pair (2). Similarly in chemistry we use a mole (6.02×10^23) for counting atoms and molecules.

In 1 Mole of anything there is 6.02×10^23 number of that thing.

i.e.

• 1 Mole of Hydrogen = 6.02×10^23 Hydrogen
• 1 Mole of NaCl = 6.02×10^23 NaCl

Molar Mass (Mass of 1 Mole) of Anything is the Gram Atomic/Molecular Mass (Atomic/Molecular Mass in grams).

i.e.

• Molar mass of Hydrogen = 1g (since atomic mass of Hydrogen is 1amu)

Similarly,

Molar mass of Calcium Carbonate = 100g

Since Molecular Mass of Calcium Carbonate is 100amu.

Now,

Number of moles

= Given mass(In grams)/Molar Mass

= 25g/100g

= 0.25

Therefore number moles in 25g of Calcium Carbonate is 0.25 moles.

Since,

Number of moles of Calcium in Calcium Carbonate is 0.25 moles.

And,

The number of moles of Oxygen in Calcium Carbonate is 0.75 moles.

Therefore,

Number of atoms = Number of moles × 1 Mole

Hence,

Number of Calcium atoms

= 0.25×6.02×10^23

= 1.5×10^23

Number of Oxygen atoms

= 0.75×6.02×10^23

= 4.5×10^23

Hence,

In 25g of Calcium Carbonate,

Number of Calcium atom is 1.5×6.02×10^23

Number of Oxygen atom is 4.5×6.02×10^23