Question

solve on paper
calculate the number of molecules in a)3 moles of sodium nitrate
b) 1.06 gram of sodium carbonate
c) 3.55 gram of clorine gas​

Answer 1

Answer:

a) The number of molecules in 3 moles of sodium nitrate is 18.066 × 10²³.

b) The number of molecules in 1.06 gram of sodium carbonate is 6022 × 10¹⁸.

c) The number of molecules in 3.55 gram of chlorine gas is 3011 × 10¹⁹.

Explanation:

a)

We have to calculate the number of molecules in 3 moles of sodium nitrate.

We know that,

Number of molecules = Number of moles × Avogadro's number

⇒ Number of molecules of sodium nitrate = n × Nᴀ

⇒ Number of molecules of sodium nitrate = 3 × 6.022 × 10²³

⇒ Number of molecules of sodium nitrate = 18.066 × 10²³

∴ The number of molecules in 3 moles of sodium nitrate is 18.066 × 10²³.

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b)

We have to calculate the number of molecules in 1.06 gram of sodium carbonate.

Now, we know that,

Molecular formula of sodium carbonate = Na₂CO₃

∴ Molar mass of sodium carbonate = [ ( 2 × Atomic mass of sodium ) + ( 1 × Atomic mass of carbon ) + ( 3 × Atomic mass of oxygen ) ]

⇒ Molar mass of sodium carbonate = [ ( 2 × 23 ) + ( 1 × 12 ) + ( 3 × 16 ) ]

⇒ Molar mass of sodium carbonate = ( 46 + 12 + 48 )

⇒ Molar mass of sodium carbonate = 106 g mol¯¹

Now,

Number of moles of sodium carbonate = ( Mass of sodium carbonate ) / ( Molar mass of sodium carbonate )

⇒ Number of moles of sodium carbonate = 1.06 g / 106 g mol¯¹

⇒ Number of moles of sodium carbonate = 1.06 ÷ 106 mol

⇒ Number of moles of sodium carbonate = 0.01 mol

Now,

Number of molecules of sodium carbonate = Number of moles × Avogadro's number

⇒ Number of molecules of sodium carbonate = n × Nᴀ

⇒ Number of molecules of sodium carbonate = 0.01 × 6.022 × 10²³

⇒ Number of molecules of sodium carbonate = 0.06022 × 10²³

⇒ Number of molecules of sodium carbonate = 06022 × 10¹⁸

⇒ Number of molecules of sodium carbonate = 6022 × 10¹⁸

∴ The number of molecules in 1.06 gram of sodium carbonate is 6022 × 10¹⁸.

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c)

We have to calculate the number of molecules in 3.55 gram of chlorine gas.

Now, we know that,

Chemical formula of chlorine gas = Cl₂

∴ Molar mass of chlorine gas = ( 2 × Atomic mass of chlorine atom )

⇒ Molar mass of chlorine gas = 2 × 35.5

⇒ Molar mass of chlorine gas = 71 g mol¯¹

Now,

Number of moles of chlorine gas = ( Mass of chlorine gas ) / ( Molar mass of chlorine gas )

⇒ Number of moles of chlorine gas = 3.55 g / 71 g mol¯¹

⇒ Number of moles of chlorine gas = 0.05 mol

Now,

Number of molecules of chlorine gas = Number of moles × Avogadro's number

⇒ Number of molecules of chlorine gas = n × Nᴀ

⇒ Number of molecules of chlorine gas = 0.05 × 6.022 × 10²³

⇒ Number of molecules of chlorine gas = 0.3011 × 10²³

⇒ Number of molecules of chlorine gas = 3011 × 10¹⁹

∴ The number of molecules in 3.55 gram of chlorine gas is 3011 × 10¹⁹.