Question

How many moles of PCl5 can be produced from 21.0 g of P4

Answer 1

Given:

21.0 grams of White Phosphorous (P4) are reacted with the required amount of Cl2 to give PCl5.

To find:

Number of moles of PCl5 produced = ?

Concepts Applied:

• Mole concept

• Molar mass

Equation for reaction:

P4 + 10Cl2 ----------> 4PCl5

Understanding the equation:

=> From the balanced chemical equation, it is clear that:

• 1 part of P4 reacts with
• 10 parts of Cl2 to give
• 4 parts of PCl5.

Let's first find the molar masses of P4 and PCl5:

Molar mass of P4 = 4 * 31 => 124 grams per mole

Molar mass of of PCl5 = 31 + 5 * 35.5 => 208.5 grams per mole

So, 21.0 grams of P4 is:

=> 21/124 moles of P4 => 0.169 moles of P4 are reacted.

Co-relating this with the equation, we get,

1 part of P4 = 0.169 moles of P4

So, 4 parts of PCl5 is 4 * 0.169 moles => 0.676 moles of PCl5

We know that 1 mole of PCl5 has a mass = 208.5 grams.

So, 0.676 moles has a mass = 208.5 * 0.676 => 140.946 grams.

Answer:

=> Thus, about 0.676 moles of PCl5 is produced.

=> This has a mass of 140.946 grams (approx.)

Additional Information:

=> 1 mole of any substance has 6.022 * 10²³ molecules/atoms/ions in it.

=> 1 mole of any gas at STP conditions has a volume of 22.4 litres.

=> STP conditions are : 1 atm Pressure ( 1.013 x 10⁵ Pa) and 273 K Temperature ( 0 °C ) .

=> NTP conditions are : 1 atm Pressure and 298 K Temperature ( 25  °C ).