Solution STOICHIOMETRY!!!

(Hooray!)

Joke… (so you’d better laugh!)

Everyone has problems…

But Chemistry students have

SOLUTIONS!!!

Stoich. again?!?

• Lots of important reactions happen in solution!

– SO… we need to know how to do stoich calculations !

– Good News: Most of the steps are the same!

Steps for Solution Stoich1. Write the balanced equation (Hint: if ions are

involved, writing the net ionic equation will be very helpful!)

2. Start with the given volume3. Use molarity (mol solute/L solution) to convert

volumemoles4. MOLE RATIO!!!5. Convert from moles to the desired units using

molarity or molar mass

Example:• When Ba(NO3)2 and K2CrO4 react in aqueous

solution, the yellow solid BaCrO4 is formed.– Calculate the mass of BaCrO4 that forms when

excess solid Ba(NO3)2 is dissolved in 265 mL of 0.0100 M K2CrO4 solution.

Net Ionic Equation:

Ba2+ (aq) + CrO4

2- (aq) BaCrO4 (s)

Convert given volume to moles:

265 mL K2CrO4 x 1L x 0.0100mol =

1000mL 1 L

2.65x10-3 mol K2CrO4

Mole Ratio(s):

2.65x10-3 mol K2CrO4 x 1 mol CrO42- x 1 mol BaCrO4

1 mol K2CrO4 1 mol CrO42-

2.65x10-3 mol BaCrO4

Convert to desired units (grams for this problem!)

2.65x10-3 mol BaCrO4 x 253.3 g BaCrO4 =

1 mol BaCrO4

0.671 g BaCrO4