How many grams are in 8.23 moles of sodium oxide?
2 answers:
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Explanation:
Step 1:
A good first step for a problem like this is to write down the chemical formula and balance it.
It appears here that we have 10.5 mL of vinegar, which IS acetic acid, and 19.13 mL of 0.460 M NaOH. That will give us the following balanced chemical equation:
CH3COOH + NaOH ------> NaCH3COO + H2O
All of the constituents come out to a value of 1, conveniently.
Step 2:
Since all of our stoichiometric coefficients are one, we can use a shortcut to answer this equation. I don't know if it has a name, but I just call it the titration formula. It goes something like this:
M1 * V1 = M2 * V2
M stands for Molarity and V stands for volume. 1 and 2 being the before the reaction and after the reaction.
So, our M1 for this is going to be what the question says was used for this titration. That's 0.460M NaOH.
Our V1 is going to be the initial volume of the sample, which was 10.5 mL
Our V2 is going to be 19.13, which is the volume when we're finished.
It's clear that we don't know M2, so let's find it.
Keep in mind that it's easier to convert to liters pretty much always, so I've done that by dividing the mL values each by 1000.
Using some algebra, we can see that we now have:
0.460 M * 0.0105 L = x M * 0.01913 L
Which goes to:
Answer:
(a) 0.779 mol Cr₂O₃
(b) 118 g Cr₂O₃
Explanation:
Step 1: Convert 156 g Cr₂S₃ to moles
Cr Molar Mass - 52.00 g/mol × 2 = 104.00 g/mol
S Molar Mass - 32.07 g/mol × 3 = 96.21 g/mol
156 g Cr₂S₃ ÷ 200.21 g/mol = 0.779182 mol Cr₂S₃
Step 2: Find conversion from Cr₂S₃ to Cr₂O₃
1 mol Cr₂S₃ equals 1 mol Cr₂O₃
Step 3: Use Dimensional Analysis
0.779182 mol Cr₂S₃ · = 0.779182 mol Cr₂O₃
0.779182 mol Cr₂O₃ ≈ 0.779 mol Cr₂O₃ (3 significant figures)
Step 4: Convert moles to grams
Cr Molar Mass - 52.00 g/mol × 2 = 104.00 g/mol
O Molar Mass - 16.00 g/mol × 3 = 48.00 g/mol
0.779182 mol Cr₂O₃ · 152.00 g/mol = 118.436 g Cr₂O₃
118.436 g Cr₂O₃ ≈ 118 g Cr₂O₃ (3 significant figures)