In the gravimetric determination of barium as 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?
50 ml of sample solution+10ml of 6M acetic acid+10ml of 3M of Ammonium acetate+heat to boiling+slight excess of 10% ammonium chromate solution+cool+filter+wash the ppt+weight+calculate the ba % in bacro4
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?
To determine the weight of the sample required for gravimetric determination of barium as BaCrO4, we need to consider the stoichiometry of the reaction and the desired result of multiplying the weight of the precipitate by 100 to obtain the percentage of barium in the sample.
In this case, the equation for the reaction is:
Ba2+ (aq) + CrO4^2- (aq) → BaCrO4 (s)
From the equation, we see that 1 mole of Ba2+ reacts with 1 mole of CrO4^2- to form 1 mole of BaCrO4. This means the molar ratio between Ba and BaCrO4 is 1:1.
To calculate the weight of the sample, we need to relate the weight of the precipitate (BaCrO4) to the weight of the barium in the sample.
Let:
W(sample) = weight of the sample in grams
W(precipitate) = weight of the precipitate (BaCrO4) in grams
% Ba = percentage of barium in the sample
From the given information, we know that:
W(precipitate) x 100 = % Ba
However, we need to consider the molecular weight of BaCrO4 to convert mass to moles. The molecular weight of BaCrO4 is:
1 Ba + 1 Cr + 4 O = 137.33 g/mol
So, the weight of Ba in the precipitate can be calculated as follows:
Weight of Ba = (W(precipitate) x 100) x (atomic weight of Ba) / (molecular weight of BaCrO4)
Now, we need to relate the weight of Ba to the weight of the sample:
Weight of Ba = (Weight of Ba / Weight of Sample) x 100
Substituting the previous equation, we get:
(Weight of Ba / Weight of Sample) x 100 = (W(precipitate) x 100) x (atomic weight of Ba) / (molecular weight of BaCrO4)
Now, let's rearrange the equation to solve for the weight of the sample:
Weight of Sample = (Weight of BaCrO4 x atomic weight of Ba) / [(W(precipitate) x atomic weight of Ba) / (molecular weight of BaCrO4)]
Finally, substitute the molecular weight values and solve for the weight of the sample in grams.