Question
How do you calculate the quantity in mol and grams of the reactants, when given the mass in mL of the product?
Answers
DrBob222
You would have done well to furnish an example AND do you know how to work a stoichiometry problem otherwise? Not much difference.
Example: Calculate the grams (and moles) of H2 needed to produce 100 mL of H2O when reacted with H2 gas @ STP. Assume density of H2O is 1.00g/mL.
..............2H2 + O2 ==> 2H2O
So you want 100 mL H2O. With a density of H2O of 1.00 g/mL that means you want 100 g. How many moles is that? That's mols = g/molar mass = 100 g x (1 mol/18 g) = 55.5
How many moles H2 on the reactant side is necessary to do that? That's
55.5 g H2O x (2 mols H2/2 moles H2O) = 55.5 mols H2 needed.
Now convert that to grams H2. g H2 = moles H2 x molar mass H2 = ?
If this isn't exactly what you wanted post something of your choice and I'll take another crack at it. Remember that are two ways to arrive at moles.
moles of a solid = grams/molar mass = ?
moles of a solution = M x L = molarity x liters = ?
If you have a solution with a density you convert to grams first (mass = volume x density then use mass/molar mass to get moles.
Example: Calculate the grams (and moles) of H2 needed to produce 100 mL of H2O when reacted with H2 gas @ STP. Assume density of H2O is 1.00g/mL.
..............2H2 + O2 ==> 2H2O
So you want 100 mL H2O. With a density of H2O of 1.00 g/mL that means you want 100 g. How many moles is that? That's mols = g/molar mass = 100 g x (1 mol/18 g) = 55.5
How many moles H2 on the reactant side is necessary to do that? That's
55.5 g H2O x (2 mols H2/2 moles H2O) = 55.5 mols H2 needed.
Now convert that to grams H2. g H2 = moles H2 x molar mass H2 = ?
If this isn't exactly what you wanted post something of your choice and I'll take another crack at it. Remember that are two ways to arrive at moles.
moles of a solid = grams/molar mass = ?
moles of a solution = M x L = molarity x liters = ?
If you have a solution with a density you convert to grams first (mass = volume x density then use mass/molar mass to get moles.