7) Calculate the weight of potassium nitrite formed due to thermal decomposition of 15.15 g of potassium nitrate.
Answers
we have to calculate the weight of potassium nitrite formed due to thermal decomposition of 15.15 g of potassium nitrate.
solution : chemical formula of potassium nitrite = KNO₂
chemical formula of potassium nitrate = KNO₃
we know, when heat is supplied to potassium nitrate, it decomposes into potassium nitrite and oxygen gas.
i.e., 2KNO₃ ⇒ 2KNO₂ + O₂
you see, two moles of KNO₃ decomposes into 2 moles KNO₂ and one mole O₂ gas.
it means, no of moles of KNO₃ decomposed = no of moles of KNO₂ formed
⇒ given weight/ molecular weight of KNO₃ = weight of KNO₂/molecular weight of KNO₂
⇒ 15.15/101 = weight of KNO₂/85
⇒ weight of KNO₂ = 15.15 × 85/101 = 12.75g
therefore the weight of potassium nitrite formed due to thermal decomposition of 15.15g of potassium nitrate is 12.75g