Answer:
1. 42.75 grams KOH
2. Add 150ml of water to the 250ml containing 9.8 grams 42.75 grams KOH
Explanation
1. moles KOH in 500ml in 1.5M solution = 0.500L x 1.5 mole/Liter = 0.75 mol KOH
grams KOH in 0.75 mole = 0.75 mole x 57 grams/mole = 42.75 grams KOH
2. formula weight H₃PO₄ = 98 grams/mole
9.8 grams H₃PO₄ in 250ml H₂O => 9.8g/98g·mole⁻¹/0.250Liters = 0.40M in H₃PO₄
Final volume of 0.25M H₃PO₄ solution = (0.40M)(250ml)/(0.25M) = 400ml
∴ Add 400ml - 250ml = 150ml of water to the 250ml of 0.40M H₃PO₄ solution => 400ml of 0.25M H₃PO₄ solution.
