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Chemistry problem of the day ...

 
 
Gouki
 
Reply Tue 21 Jun, 2005 04:19 pm
A mixture is prepared by adding 25 mL of 0.185 M Na3PO4 to 34 mL of 0.140 M Ca(NO3)2

a) what mass of Ca3(PO4)2 will be formed?
b) what will be the concentrations of ecah of the ions in the mixture after reaction?

thanks in advance
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raprap
 
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Reply Tue 21 Jun, 2005 05:50 pm
First you must complete the reaction

2Na3PO4+3Ca(NO3)2->Ca3(PO4)2+6NaNO3

The determine the quantity of reactants (the left)
25ml*0.185moles/1000ml Na3PO4 (0.004625 mole)
34ml*0.140moles/1000ml Ca(NO3)2 ( 0.00476 mole)

Now determine the limiting reactant [Looks like Ca(NO3)2]

so (0.00476/3 (0.001587) moles of Ca3(PO4)2 and 6*0.001587 (0.00952) moles of NaNO3 will be formed, and 0.004625-0.00476*2/3 (0.001452) moles of Na3PO4 will be left.

And what is the total volume? its 59 (25+34)ml, right. And how many liters is this? Its 59/1000 (0.059 liter right?)

So the molar concentrations after reaction are
0.001587/0.059 M Ca3(PO4)2
0.00952/0.059 M NaNO3
and
0.001452/0.059 M Na3PO4
Right

But if I were you I'd check my arithmetic--

Rap
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Gouki
 
  1  
Reply Tue 21 Jun, 2005 06:27 pm
raprap wrote:
First you must complete the reaction

2Na3PO4+3Ca(NO3)2->Ca3(PO4)2+6NaNO3

The determine the quantity of reactants (the left)
25ml*0.185moles/1000ml Na3PO4 (0.004625 mole)
34ml*0.140moles/1000ml Ca(NO3)2 ( 0.00476 mole)

Now determine the limiting reactant [Looks like Ca(NO3)2]

so (0.00476/3 (0.001587) moles of Ca3(PO4)2 and 6*0.001587 (0.00952) moles of NaNO3 will be formed, and 0.004625-0.00476*2/3 (0.001452) moles of Na3PO4 will be left.

And what is the total volume? its 59 (25+34)ml, right. And how many liters is this? Its 59/1000 (0.059 liter right?)

So the molar concentrations after reaction are
0.001587/0.059 M Ca3(PO4)2
0.00952/0.059 M NaNO3
and
0.001452/0.059 M Na3PO4
Right

But if I were you I'd check my arithmetic--

Rap


thank you for your reply. not the first time you've helped me out here. pardon me for not having stated my question clearly. I actually wanted to find the concentration of each ion after the reaction. Confused thanks
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