Hello, I am having trouble with a question from my chem lab. Here is my data
Weight of empty crucible and cover = 21.113 g
Weight of crucible, cover, MgO and Mg3N2 = 21.906 g
Weight of crucible, cover, MgOand addition of H2O and heat =21.909 g
The change in mass is 0.00300 g (I got that much right)
Calculate the number of moles of Mg3N2. (i cant figure this out)
ive been given the equations:
change in mass (grams) = grams Mg0 - grams Mg3N2 reacted
and the equation
Mg3N2 (s) + 3H20 (l) --> 3MgO (s) + 2NH3
MgO is 60.3% Mg. Mg3N2 is about 72% Mg
Mg3N2 with water added changes to Mg(OH)2 which is then is changed to MgO upon heating. For a small sample, the overall weight changes are quite small. You would need very precise lab results to make accurate calculations of the % of Mg3N2. There is some algebra involved. Your results indicate that you had only a trace of Mg3N2, the dark product mixed in with the major product, MgO, which is white. I don't see much point in doing elaborate calculations based on not so precise measurements about a trace of biproduct
To calculate the number of moles of Mg3N2, we need to use the information provided and apply stoichiometry principles. Let's break down the steps to solve the problem:
1. Calculate the mass of Mg3N2 reacted:
Change in mass = grams MgO - grams Mg3N2
Given that the change in mass is 0.00300 g, we can substitute this value into the equation:
0.00300 g = grams MgO - grams Mg3N2
2. Calculate the molar mass of MgO and Mg3N2:
The molar mass of an element or compound is the mass of one mole of that substance.
The molar mass of MgO is 40.31 g/mol (atomic mass of Mg + atomic mass of O), and the molar mass of Mg3N2 is 100.93 g/mol (atomic mass of Mg multiplied by 3 + atomic mass of N multiplied by 2).
3. Calculate the number of moles of Mg3N2:
To do this, we need to convert the masses of MgO and Mg3N2 into moles.
moles = mass / molar mass
moles of Mg3N2 = grams Mg3N2 / molar mass of Mg3N2
Plug in the values from step 1 and 2:
moles of Mg3N2 = 0.00300 g / 100.93 g/mol
Calculate this value to find the number of moles of Mg3N2.
Remember, it's important to double-check the stoichiometry coefficients in the balanced chemical equation. In this case, the stoichiometry coefficients are 1:3 for Mg3N2:MgO.