Question

A Solution contains 58.5g of common salt in 360g of water.

Calculate the total number of protons in the solution.

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Answer 1

A solution contains 58.5 g of common salt in 360g of water.

We have to find the total number of protons in the solution.

no of moles of common salt = mass of common salt/molar mass of it.

= $\frac{58.5g}{58.5g/mol}$

= 1 mol

no of NaCl molecules = no of moles of NaCl × Avogadro's number

= 1 × 6.023 × 10²³

= 6.023 × 10²³

∵ 1 molecule of NaCl contains (23 + 17) = 40 protons

[ note : number of protons of an atom is atomic number of that atom. ]

∴ number of protons in NaCl molecules = 40 × 6.023 × 10²³

= 24.092 × 10²³

= 2.4092 × 10²⁴

no of moles of water = mass of water/molar mass of water

= $\frac{360g}{18g/mol}$

= 20 mol

no of water molecules = no of moles of water × Avogadro's number

= 20 × 6.023 × 10²³

= 1.2046 × 10²⁴

∵ 1 molecule of water contains (2 + 8) = 10 protons.

∴ number of protons in water molecules = 10 × no of water molecules

= 10 × 1.2046 × 10²³

= 12.046 × 10²⁴

∴ Total number of protons in the solution = number of protons in common salt + number of protons in water

= 2.4092 × 10²⁴ + 12.046 × 10²⁴

= 14.4552 × 10²⁴

= 1.44552 × 10²⁵

Therefore the total number of protons in the solution is 1.44552 × 10²⁵