# chemistry 1046

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A.Determine the pH of the solution.

a solution that is 1.17% HCl by mass (Assume a density of 1.01 g/mL for the solution.)

B. Amphetamine (C9H13N) is a weak base with a pKb of 4.2. Calculate the pH of a solution containing an amphetamine concentration of 279 mg/L.

• chemistry 1046 -

A.
1.17% by mass means 1.17g HCl/100 g soln.
mols HCl = grams/molar mass
Convert 100 g to mL using density.
Then M = mols/L

B. To save typing let's call amphetamine BNH2. M BNH2 = 0.279/molar mass = ?
..........BNH2 + HOH ==> BNH3^+ + OH^-
I.........?..............0.........0
C........-x..............x.........x
E.........?-x.............x.........x

Substitute from the ICE chart into the Kb expression for amphetamine and solve for x = OH^-, then convert that to pH.

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