marco starts with 100g of zinc and 150g of sulfuric acid. at the end of the reaction, marco finds the mass of the contents of the beaker is 247g. he repeats the experiment and gets the same result. has he made a mistake. suggest why he got this result.
Answers
Given info : Marco starts with 100g of zinc and 150g of sulfuric acid. at the end of the reaction, marco finds the mass of the contents of the beaker is 247g. he repeats the experiment and gets the same result.
To check : has he made a mistake ? suggest why he got this result.
solution : we know, when zinc is reacted with sulphuric acid, it forms zinc sulphate and hydrogen gas.
Zn + H₂SO₄ ⇒ZnSO₄ + H₂ (↑)
here one mole of Zinc reacts with one mole of sulphric acid and evolves one mole of hydrogen gas.
let's find how much hydrogen gas has evolved during reaction.
atomic mass of zinc = 65.38 g/mol
given mass of zinc = 100 g
so no of moles of zinc = 100/65.38 ≈ 1.5
similarly, given mass of sulphuric acid = 150g
molecular mass of sulphuric acid = 98.079 g/mol
so no of moles of sulphuric acid = 150/98.079 ≈ 1.53
no of moles of hydrogen gas = no of moles of zinc = no of moles of sulphuric acid = 1.5
mass of hydrogen gas = moles × molar mass
= 1.5 × 2 = 3 g
Therefore 3g of hydrogen gas has evolved during the reaction that's why Marco gets 247 g instead of 250g (100g of zinc + 150g of sulphuric acid ). and hence Marco gets this result due to evolving of hydrogen gas.