Question

calculate the no. of atoms in 9g of water
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Answer 1

Answer:

3.011×10²³ molecules of H2O

Step-by-step explanation:

Molecular mass of H2O =18g

Given mass=9g

no. of moles = given mass/ molecular mass

= 9/18 = 0.5 moles

No. of molecules = no. of moles× Avogadro no.

=0.5× 6.022×10²³

=3.011×10²³ molecules

Answer 2

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Given:

9 gram of water

To find:

Number of atoms in water

Explanation:

Molecular formula of water is H2O

Molar mass of H2O = 2×1 + 16 = 18 gram

Mass of H20 = 9 gram

$\\ Mole = \dfrac{mass}{molar \:mass} \\ \\ = \dfrac{9}{18} \\ \\ = 0.5 \: mole \: of \: water$

1 mole of water contain 3 × 6.02 × 10 ^ 23 atoms ( 2 atom of hydrogen and 1 atom of oxygen)

0.5 mole water contain

$\\ = \dfrac{0.5 \times 3 \times 6.02 \times 10 {}^{23} }{1} \\ \\ = 9.03 \times 10 {}^{23} \: atoms$

Required answer:

Therefore, 9gram of water contain 9.03 × 10^23 atoms

Basic points:

• 1 mole contain 6.02 × 10^23 molecules
• 1 mole contain Number of atoms× 6.02 × 10^23 atoms
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