A chemist weighed out 5.31 g of a mixture containing unknown amounts of BaO(s) and CaO(s) and placed the sample in a 1.50 L flask containing CO2(g) at 30.0°C and 750. torr. After the reaction to form BaCO3(s) and CaCO3(s) was completed, the pressure of CO2(g) remaining was 230. torr. Calculate the mass percents of CaO(s) and BaO(s) in the mixture.
Use PV = nRT, substitute the numbers, and calculate mols CO2 initially, redo the formula and recalculate with new numbers to determine the moles CO2 remaining. The difference equals moles CO2 reacted.
Then let X = mass BaO
Let Y = mass CaO.
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X + Y = 5.31
(X/molar mass BaO) + (Y/molar mass CaO) = moles CO2 consumed (from above.)
Solve the two simultaneous equations for X and Y,
Then %BaO = (mass BaO/5.31)*100 = ??
%CaO = (mass CaO/5.31)*100 = ??
Post your work if you get stuck.
i have a hard time understanding how to calculate the moles of CO2 remaining?
how do you use the PV=nRT for the remaining CO2?
The problem states that after the CO2 has reacted with BaO and CaO, the remaining pressure is 230 torr. So plug that back into PV = nRT for P, along with the other numbers, and calculate a new n. Subtracting the two will give you the amount that reacted.
for T, do I have to convert C to Kelvin? would they yield the same answers?
X + Y = 5.31
(X/molar mass BaO) + (Y/molar mass CaO) = moles CO2 consumed (from above.)
Solve the two simultaneous equations for X and Y,
^I don't really understand this part either.
why is moles of CO2 consumed equal to the combined moles of BaO and CaO?
To calculate the mass percentages of CaO(s) and BaO(s) in the mixture, we need to use the ideal gas law and stoichiometry to determine the moles of CO2(g) reacted and then use them to find the moles of CaO(s) and BaO(s).
Let's break down the steps:
1. Calculate the initial moles of CO2(g):
- Convert the given pressure to atm: 750. torr = 750. torr * (1 atm / 760 torr) = 0.987 atm
- Use the ideal gas law equation: PV = nRT
- Rearrange the equation to solve for moles (n): n = PV / RT
- Plug in the values: n = (0.987 atm * 1.50 L) / (0.0821 atm L/mol K * 30.0 + 273 K)
- Calculate the initial moles of CO2(g).
2. Calculate the final moles of CO2(g):
- Convert the final pressure to atm: 230. torr = 230. torr * (1 atm / 760 torr) = 0.303 atm
- Use the ideal gas law equation: PV = nRT
- Rearrange the equation to solve for moles (n): n = PV / RT
- Plug in the values: n = (0.303 atm * 1.50 L) / (0.0821 atm L/mol K * 30.0 + 273 K)
- Calculate the final moles of CO2(g).
3. Calculate the moles of CO2(g) reacted:
- Subtract the final moles of CO2(g) from the initial moles of CO2(g).
- You now have the moles of CO2(g) reacted.
4. Use stoichiometry to find the moles of CaO(s) and BaO(s):
- The balanced equation for the reaction is: BaO(s) + CaO(s) + CO2(g) → BaCO3(s) + CaCO3(s)
- From the balanced equation, we know that the molar ratio between CO2 and CaO is 1:1, and CO2 and BaO is also 1:1.
- Use this ratio to determine the moles of CaO(s) and BaO(s) reacted.
5. Calculate the mass percent of CaO(s) and BaO(s):
- The mass percent of CaO(s) can be calculated using the formula: (mass of CaO / mass of the mixture) * 100%
- The mass percent of BaO(s) can be calculated using the formula: (mass of BaO / mass of the mixture) * 100%
6. Calculate the actual masses of CaO and BaO in the mixture:
- Convert moles to grams using the molar masses of CaO(s) and BaO(s).
- Calculate the actual mass of CaO(s) and BaO(s) in the mixture.
By following these steps, you should be able to calculate the mass percentages of CaO(s) and BaO(s) in the mixture.