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### Topic: Dilution problem  (Read 7428 times)

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#### sarahjane

• Guest ##### Dilution problem
« on: March 22, 2004, 04:21:42 AM »
how do you calculate the amount of potassium dichromate required to make 250mLs of a 0.15M solution
« Last Edit: April 24, 2004, 07:14:21 PM by hmx9123 »

#### gregpawin

• Chemist
• Full Member
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• Mole Snacks: +22/-5
• Gender: • Ebichu chu chu chuses you! ##### Re:how do you calculate an amount required to make up a solution
« Reply #1 on: March 22, 2004, 06:17:33 PM »
Simply enough, molarity is just the measure of the number of moles of a solute in liters of a solvent.  So molarity (M) is equal to the number of moles of solute divided by the liters of solvent.  M=n/V where n are moles of solute and V is the number of liters of solvent.  There are three variables here.  The problem has given you two of the variables, so you can solve it.  0.15M=n/0.250L so n = 0.0375moles of K2Cr2O7.

I'm probably sure they'll want you to convert it into grams so just multiply it by the molar mass.
« Last Edit: March 22, 2004, 06:18:30 PM by gregpawin »
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