home > q&a board > chemistry > topic: molarity problem

Q BgQuestion:

Scholar
Karma Points: 200
Respect (95%):
posted by  k8 on 10/9/2008 11:26:24 AM  |  status: Live  

Molarity problem

Course Textbook Chapter Problem
N/A Tro's book 4 444
Question Details:
A scientist wants to make a solution for tribasic sodium phosphate Na3PO4, for a lab experiment. How many grams of Na3PO4 will be needed to produce 375mL of a solution that has a concentration of Na+ions of 0.800 M?   How many moles of Na+ are in the solution?
 
Mass of Na3PO4 in grams g
 
I am lost with this problem. I really need help. Will rate. Thanks K8
Tags: Chemistry
Bonus Point Alert! Earn +2 additional karma points for helping this monthly member.

AAnswers:

Answer Question
Sage
Karma Points: 3,622
(UCLA)
posted by PubStomp on 10/9/2008 11:31:02 AM  |  status: Live
Asker's Rating: Lifesaver   
k8's comment:
"Thank you"
Response Details:
so there will be 3 Na+ ions per mole of Na3PO4

You need .8 * .375 = .3 moles of Na3PO4 to have .8 Molarity if there were only 1 Na+

but since there are 3 you divide by 3 to have .1 Moles of Na3PO4


Molar mass of Na3PO4 = 163.940671 g/mol

so .1 * Molar mass of Na3PO4 = 163.940671 g/mol

= 16.4 grams of Na3PO4

Inevitable
Answer Question
Ask New Question

Join Cramster's Community

Cramster.com brings together students, educators and subject enthusiasts in an online study community. With around-the-clock expert help and a community of over 100,000 knowledgeable members, you can find the help you need, whenever you need it. Join for free today » How Cramster is different from tutoring »

Need Help In

Useful Links