heres another chem question im having trouble on...thank you so much~
A 750. mL solution containing potassium bromide is evaporated to dryness and 133.74 milligrams of solid potassium bromide are collected. What was the molarity of the original solution?
(answer in moles)
2007-08-07 11:31:06 · 2 answers · asked by Anonymous in Science & Mathematics ➔ Chemistry
Molarity = (moles solute)/(liter solution)
Given( assume bone dry) : 133.74 mg potassium bromide
Volume solution = 750 ml
Weight/M.Weight of potassium bromide = (133.74/(39+80) =1.12
Molarity = 1.12/750 = 1.5X10^-3 millimoles/ml
= 1.5X10^ -3moles/ liter or 1.5X^-3 molar
2007-08-07 12:08:01 · answer #1 · answered by supermontero2000 2 · 0⤊ 0⤋
Atomic weights: K=39 Br=80 KBr=119
Let the solution be called S
Let a milligram molecular weight be called a mmol
133.74mgKBr/750mLS x 1mmolKBr/119mgKBr x 1molKBr/1000mmolKBr x 1000mLS/1LS = 0.00149M
2007-08-07 19:07:38 · answer #2 · answered by steve_geo1 7 · 0⤊ 0⤋