Homework Help: chemistry

Posted by Jordin on Tuesday, October 5, 2010 at 1:30pm.

A 0.2528 g sample of a mixture containing sodium carbonate and sand requires 12.32 mL of 0.2409 M HCl(aq). Assuming that the sand does not react with the HCl(aq), what percentage of the mixture is sodium carbonate?

Balanced equation:
Na2CO3(s) + 2 HCl(aq) Би 2 NaCl(aq) + CO2(g) + H2O(l)

chemistry - DrBob222, Tuesday, October 5, 2010 at 1:44pm
moles HCl = M x L = ??
moles Na2CO3 = 1/2 moles HCl (from the equation).
g Na2CO3 = moles x molar mass

%Na2CO3 = (mass Na2CO3/mass sample)*100 = ??
chemistry - Jordin, Tuesday, October 5, 2010 at 1:52pm
Thank you! So, is this correct?

moles HCl = M x L
= .2409 X .01232 = .00297

moles Na2CO3 = 1/2 moles HCl (from the equation).
= .00297 / 2 = .00148

g Na2CO3 = moles x molar mass
.00148 X 106 = .157

%Na2CO3 = (mass Na2CO3/mass sample)*100 = ??
.157 / .2528 X 100 = 60.8%
chemistry - DrBob222, Tuesday, October 5, 2010 at 2:15pm
Almost but not quite.
1. When multiplying 0.2409 x 0.01232, the answer is 0.00296788. There are two things wrong here. First, you threw away at least one significant figure (both numbers you multiplied have four figures so you are allowed four in the answer but you have only three). I leave all of that in the calculator and use it as is in the next calculation. You COULD round at this point to 0.002968 but I recommend you leave all of the numbers in the calculator and go to the next step.
You need to go through and correct the other steps.
2. I think you punched in the wrong numbers for the last step because
(0.157/0.2528)*100 = = 62.10%.

If we go through it all at once as follows, I get this
(0.2409 x 0.01232 x 1/2 x 105.99/0.2528)*100 = 62.21647 which rounds to 62.22% to four significant figures.
chemistry - Jordin, Tuesday, October 5, 2010 at 2:22pm
Oh ok, I see what I did now. Thank you for the help! : )

Answer this Question

Related Questions

science - if i had mixture of sodium carbonate and sand, and spilled some sodium...
Chemistry - In an experiment to find the percentage of calcium carbonate in ...
Chemistry - 2.500g sample of a mixture of sodium carbonate and sodium chloride ...
Chemistry - calculate the mass percent of sand, sodium chloride and copper(ll) ...
chem - "The percentage of sodium hydrogen carbonate, NaHCO3, in a powder ...
chemistry - The pH of saturated Sr(OH)2 (aq) is found to be 13.12. A 10.0 mL ...
Science - Calculate the mass percent of sand, sodium chloride and copper (II) ...
Chemistry - Suppose that you calculated the mass percent of sand in the mixture ...
Chemistry - a 110 g solid sample that is a mixture of CaCO3 and CaCl2 is reacted...
Chemistry - Devise a way to separate sand from a mixture of charcoal, sand, ...

For Further Reading

First Name:
School Subject:
Answer: