in the gravimetric determination of barium in BaCrO4, what weight of sample must be taken so that the weight of the precipitate in milligrams multiplied by 100 will equal the % Ba in the sample?
[mass BaCrO4 ppt x (atomic mass Ba/molar mass BaCrO4)/mass sample)]*100 = %Ba
For mass BaCrO4 substitute the following:
(mg BaSO4 x 100/1000) into the top equation and solve for mass sample.
Post your work if you get stuck.
To calculate the weight of the sample needed in gravimetric determination, we need to consider the stoichiometry of the reaction, the molar mass of BaCrO4, and the desired percent of Ba in the sample.
1. Determine the desired percent of Ba in the sample. Let's assume it is x% Ba.
2. Convert the desired percent to a decimal by dividing by 100: x/100.
3. Consider the stoichiometry of the reaction between BaCrO4 and Ba.
The balanced chemical equation is:
BaCrO4 (s) + 2 Ba(NO3)2 (aq) → 3 Ba(NO3)2BaCrO4 (s)
From the equation, we can see that for every 1 mole of BaCrO4, we obtain 3 moles of Ba.
4. Determine the molar mass of BaCrO4. The molar mass of Ba is 137.33 g/mol, Cr is 51.996 g/mol, and O is 16.00 g/mol. Therefore, the molar mass of BaCrO4 is calculated as follows:
Molar mass of BaCrO4 = (137.33 g/mol) + (51.996 g/mol) + (4 * 16.00 g/mol)
5. Calculate the weight of the BaCrO4 precipitate in milligrams that will provide the desired percentage of Ba in the sample.
Weight of BaCrO4 (mg) = (x/100) * (mol Ba/MW BaCrO4) * (MW BaCrO4)
Let's plug in the values:
Weight of BaCrO4 (mg) = (x/100) * (3 mol Ba / 1 mol BaCrO4) * (Molar mass of BaCrO4)
Simplifying further:
Weight of BaCrO4 (mg) = (x/100) * 3 * (Molar mass of BaCrO4)
6. Finally, we need to multiply the weight of the BaCrO4 precipitate by 100 to fulfill the requirement mentioned in the question.
Weight of sample (mg) = 100 * Weight of BaCrO4 (mg)
Please provide the desired percentage of Ba (x%) to obtain the specific value of the weight of the sample needed.
To determine the weight of the sample needed, we need to consider the stoichiometry of the reaction and the desired outcome.
In the gravimetric determination of barium (Ba) in BaCrO4, the reaction involves the precipitation of BaCrO4:
BaCrO4(s) → Ba2+(aq) + CrO4^2-(aq)
From the balanced equation, we can see that one mole of BaCrO4 produces one mole of Ba2+. Therefore, the weight of the precipitate (BaCrO4) will be equal to the weight of Ba present in the sample.
To calculate the weight of the sample needed, we'll follow these steps:
Step 1: Determine the molar mass of BaCrO4
The molar mass of BaCrO4 can be calculated by adding the atomic masses of each element in the compound. The atomic masses (in g/mol) are as follows:
Ba: 137.33 g/mol
Cr: 52.00 g/mol
O: 16.00 g/mol (there are four oxygen atoms in BaCrO4)
Total molar mass of BaCrO4 = (137.33 + 52.00 + 4 * 16.00) g/mol
Step 2: Calculate the weight of the sample
Since the weight of the precipitate (BaCrO4) is equal to the weight of Ba in the sample, we can set up the following equation:
Weight of BaCrO4 (in grams) = % Ba in the sample / 100 * Weight of the sample (in grams)
Rearranging the equation:
Weight of the sample (in grams) = (Weight of BaCrO4 (in grams) / (% Ba in the sample / 100))
Based on the given information, the weight of the precipitate (BaCrO4) needs to be multiplied by 100 to equal the % Ba in the sample:
Weight of BaCrO4 (in grams) = (% Ba in the sample / 100) * Weight of the precipitate (in milligrams) * 1 g / 1000 mg * 100
Now, substitute this value in the previously rearranged equation to find the weight of the sample (in grams):
Weight of the sample (in grams) = ((% Ba in the sample / 100) * Weight of the precipitate (in milligrams) * 1 g / 1000 mg * 100) / (% Ba in the sample / 100)
Simplifying the equation:
Weight of the sample (in grams) = (Weight of the precipitate (in milligrams) * 1 g / 10 mg)
So, to find the weight of the sample, we need to divide the weight of the precipitate (in milligrams) by 10.
Please note that this calculation assumes 100% efficiency in the precipitation reaction and neglects other factors that may affect the accuracy of the determination. Additionally, accurate determination of the % Ba in the sample requires precise measurements and careful execution of the experimental procedure.