Question

calculate the molecules of hydrogen gas occupies 0.55dm^3​

Answer 1

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The mole ratio for the reaction is 2:2:1 meaning, two moles of KClO3 yields 2 moles of KCl and 3 moles of O2

Calculate the moles of oxygen from the 6.72 dm3 given

1 dm3=1 liter 

6.72 dm3=6.72 liters of oxygen

Using the ideal gas law, which states that 1 mole of an ideal gas occupies 22.4 liters by volume we can calculate the moles of oxygen as follows:

If 22.4 liters = 1 mole

Then 6.72 liters  = 1 × 6.72/ 22.4

                           = 0.3 moles

From the equation above we found the mole ratio for the equation to be 2:2:1

That means, for 0.3 moles of oxygen to be liberated, we will need 0.3 × 2 = 0.6 moles of KClO3

Use the 0.6 moles of KClO₃ to find the mass required

Moles = mass / molar mass   

Then,

mass = molar mass × moles

molar mass of potassium chlorate is 122.5 g/mol (given) and moles is 0.6(calculated)

Therefore mass of KClO3 required   = 122.5 g/mol x 0.6 moles

                                                         = 73.5 g

Therefore you need 73.5 g of potassium chlorate to liberate 6.72 dm3  of oxygen.