Mass of plant food sample 10.500 g Mass of watch glass 5.000 g Mass of watch gla
ID: 479022 • Letter: M
Question
Mass of plant food sample 10.500 g Mass of watch glass 5.000 g Mass of watch glass and product 6.500 g Calculations 1. What is the mass of your precipitate MgNH4PO46H20)? 1.5 grams 2. What is the molecular weight of Mg 6H20? 245.41 g/mol 3. How many moles of MgNH4PO4 6H20 are in your sample? 1.5 g 245.41 g/mol 6.11x10 -3 moles 4. How many moles of P are in your sample of MgNH4PO46H20? Moles of P (moles, MgNHAPO4 6H20)(? mole P 1 mole MgNHAPO4 6H20) 6.11x1 -3 moles 5. How many grams of P are in your sample of MgNH4PO4 6H20? 6. How many grams of P are in your original fertilizer sample?Explanation / Answer
Given – Mass of food plant sample = 10.500g
Mass of watch glass = 5.000g
Mass of watch glass + product = 6.500 g
1) Mass of precipitate MgNH4PO4.6H2O is 1.5 g
2) The molecular weight of MgNH4PO4.6H2O is 245.41 g/mol
3) Moles of MgNH4PO4.6H2O = 1.5 g/245.41 g/mol
= 0.0061122 = 6.11 x 10^-3 moles.
4) Moles of P in your original sample of MgNH4PO4.6H2O
(1.5g MgNH4PO4.6H2O)(1 mol MgNH4PO4.6H2O/245.41g MgNH4PO4.6H2O) X
(1 mol P/1 mol MgNH4PO4 6H2O) = 6.11 x 10^-3 moles of P
5) g of P in your sample-
Molar mass of P = 30.97g / mol
g of P = Moles of P x Molar mass of P
6.11 x 10^-3 moles x 30.97g /mol
P = 0.18922g P
7) The percentage of phosphorous in the sample is given by the expression:
% of P = g of P/g of sample x 100
= 0.18922g /1.5g x 100 = 12.61%
8) Moles of P2O5 in original fertilizer sample-
We use this factor because there are 2 moles of P in every 1 mole of P2O5.
(1.5g MgNH4PO4.6H2O)(1 MOL MgNH4PO4 .6H2O/245.41g MgNH4PO4. 6H2O) X
(1 mol P/1 mol MgNH4PO4. 6H2O)(1mol P2O5/2 mol P) = 3.05 x 10^-3 moles P2O5
9) g of P2O5 in your sample
Molar mass of P2O5 = 141.9g /mol
G of P2O5 = 3.05 x 10^-3 moles x 141.9g/mol = 0.432g
10) The percentage of phosphorous pentoxide-
%P2O5 = (0.432g / 1.5g) x 100 = 28.4% P2O5