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Topic: Precipitation & Dilution  (Read 3648 times)

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FerndaleTiger

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Precipitation & Dilution
« on: December 06, 2004, 09:23:56 PM »
1) How many grams of precipitate are formed if 192 mL of a 0.889 M aluminum sulfate solution and 346mL of a 4.93 M sodium hydroxide solution are mixed together?

The balanced equation i found:

Al2(SO4)3 + 6 NaOH ---> 2 Al(OH)3 + 3 Na2SO4

So then I took .889 M x .192 L = .170688 mol aluminum sulfate then multiply by 2 mol Al(OH)3 over 1 mol Al2(SO4)3 multiply once more by 77.98 g Al(OH)3 over 1 mol of that = 26.6 g Al(OH)3.

The other part was 4.93 M x .346 L = 1.70578 mol Sodium hydroxide, multiply by 2 mol Al(OH)3 over 6 mol NaOH multiply again by 77.98 g Al(OH)3 over 1 mol of that = 44.4 g Al(OH)3.

Now is this a limiting reagent or something? If so I'd choose 26.6 g as the answer...Help would be appreciated.

2) You are asked to prepare 0.162 L of a solution that is 0.612 M in acetate ion. Your only source of acetate ion is a bottle of calcium acetate solution marked 1.90 M calcium acetate. What volume (mL) of the calcium acetate solution must be used.

Do i find the moles of calcium acetate by the moles = Molarity/Liters and then work my way to to something? I confused.

*Edit: The Dilution problem was setup to use the formula Mi x Vi = Mf x Vf and then convert to mL and divide by 2. I understand what I did wrong for #2.
« Last Edit: December 07, 2004, 12:20:53 AM by FerndaleTiger »

Offline AWK

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Re:Precipitation & Dilution
« Reply #1 on: December 07, 2004, 01:22:03 AM »
1. OK
2.  This formula works for acetate concentration, so double concentration of calcium acetate and result should be 26.1 mL.
AWK

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