I'm trying to figure out the percent composition of a mixture of an unknown (a combination of NaHCO3 and NaCl).
Here's my data:
Mass of 150mL of empty beaker: 80.937g
Mass of 150mL beaker w/ unknown: 81.957g
Mass of 150mL beaker w/ unknown after reaction: 89.126g
Mass of bottle of 1.00 M HCl: 172.079g
Mass of bottle of 1.00 M HCl after reaction: 164.621g
My idea of finding the percent composition is involving the calculations of turning CO2 mass into moles of CO2 to moles of NaHCO3 to mass of NaHCO3 to get the percent composition of NaHCO3. I'm not quite sure if I have got my calculations down right.
Calculation of CO2 loss (172.079g + 81.957g) - (164.621g - 89.126g) = .289g CO2
Since CO2 and NaHCO3 has a 1:1 we can do this calculation to get the mass of NaHCO3
.289g CO2 * (1 mol/44g CO2) * (84g NaHCO3/1 mol) = .5517g NaHCO3
Then the percent composition of NaHCO3 would be. (Mass of NaHCO3/ Molar mass of NaHCO3) * 100
(.5517g NaHCO3 / 84.00g NaHCO3) * 100 = .6568%
That means I have 99.34% of NaCl in the mixture if .6568% is NaHCO3. This doesn't seem logical to me.
Can you please provide an explanation on what I did wrong or where I went wrong?
Thank you !
[Update]
I think I know what I did wrong. Instead of: (Mass Sample of NaHCO3 / Molar Mass of NaHCO3) * 100 = some value, it should be (Mass Sample of NaHCO3 / Total mass sample of unknown mixture) * 100 = some value.
So, (.5517g NaHCO3 / 1.020g of unknown mixture) * 100 = 54.09% of NaHCO3
Please let me know if I have the right idea. Thank you!
To determine the percent composition of the mixture of NaHCO3 and NaCl, you've made a few mistakes in your calculations. Let's go through the correct steps:
1. Start by finding the mass of NaHCO3. To do this, subtract the mass of the empty beaker from the mass of the beaker with the unknown:
Mass of NaHCO3 = Mass of beaker with unknown - Mass of empty beaker
= 81.957g - 80.937g
= 1.02g
2. Next, calculate the moles of NaHCO3. You can use the molar mass of NaHCO3 to convert from grams to moles:
Moles of NaHCO3 = Mass of NaHCO3 / Molar mass of NaHCO3
= 1.02g / 84.00 g/mol
= 0.0121 mol
3. To find the percent composition of NaHCO3, divide the mass of NaHCO3 by the total mass of the mixture (beaker with unknown):
Percent composition of NaHCO3 = (Mass of NaHCO3 / Total mass of mixture) * 100
= (1.02g / 81.957g) * 100
= 1.24%
4. Finally, to determine the percent composition of NaCl, subtract the percent composition of NaHCO3 from 100%:
Percent composition of NaCl = 100% - Percent composition of NaHCO3
= 100% - 1.24%
= 98.76%
Therefore, the correct percent composition of NaHCO3 in the mixture is 1.24%, while the percent composition of NaCl is 98.76%.