leftover: approximately 11.73 g of sulfuric acid.explanation
which reactant is in excess?
the theoretical yield of water from al(oh)₃ is lower than that from h₂so₄. as a result,al(oh)₃ is the limiting reactant. h₂so₄ is in excess.
how many moles of h₂so₄ is consumed?
2 al(oh)₃ + 3 h₂so₄ → al₂(so₄)₃ + 6 h₂o
each mole of al(oh)₃ corresponds to 3/2 moles of h₂so4. the formula mass of al(oh)₃ is 78.003 g/mol. there are 15 / 78.003 = 0.19230 moles of al(oh)₃ in the five grams of al(oh)₃ available. al(oh)₃ is in excess, meaning that all 0.19230 moles will be consumed. accordingly, 0.19230 × 3/2 = 0.28845 moles of h₂so₄ will be consumed.
how many grams of h₂so₄ is consumed?
the molar mass of h₂so₄ is 98.076 g.mol. the mass of 0.28845 moles of h₂so₄ is 0.28845 × 98.076 = 28.289 g.
how many grams of h₂so₄ is in excess?
40 grams of sulfuric acid h₂so₄ is available. 28.289 grams is consumed. the remaining 40 - 28.289 = 11.711 g is in excess. that's closest to the first option: 11.73 g of sulfuric acid.