solution problem

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D-nice1D
Posts: 19
Joined: Fri Sep 28, 2018 12:21 am

solution problem

Postby D-nice1D » Fri Jul 05, 2019 1:36 am

A student prepared a solution of sodium carbonate by adding 2.111 g of the solid to a 250.0-mL volumetric f ask and adding water to the mark. Some of this solution was transferred to a buret. What volume of solution should the student transfer into a f ask to obtain (a) 2.15 mmol Na#; (b) 4.98 mmol CO3 2"; (c) 50.0 mg Na2CO3?

I use the MVinitia=MVfinal for this one correct??

Leah farhadi 1F
Posts: 36
Joined: Mon Jun 17, 2019 7:23 am

Re: solution problem

Postby Leah farhadi 1F » Fri Jul 05, 2019 9:28 am

For this question they give you grams of Na2CO3 and moles of solute, knowing this we would use the equation M=n/V. If we were given two molarities and a volume, then we can use M1V1=M2V2 to find the correct volume, but because we only have one molarity and moles we use M=n/V

First we take grams of Na2CO3 and find moles: 2.111g/(105.99 g.mol^-1) = 0.01992 mol Na2CO3
Then, we divide by 0.250 liters to get molarity: 0.01992/.250 = 0.07697 M
Using this information, we have 2.15 x 10^-3 mol Na, so we plug in what we know:

V = (2.15 x 10^-3)/(0.007967) x (1 mol Na2CO2/2 mol Na) = 1.35x10^-2 L

We multiple by (1/2) because we are finding moles of Na in Na2CO2


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