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Chemistry reading equations Test tomorrow really need help!!?
General question:Is the coefficient of a compound ( or whatever else can be in an equation( always the number of moles in an equation. Please be specific in your answer but try to make it easy for someone to understand who is not good in chemistry.bexplain your answers
For example o e equation says what mass of each product results if 75Oml of a 6.00 MH3PO4 reacts according to the equation H3PO4 + Ca (OH)2 arrow Ca3 ( PO4)2 + H2O? I would think you could just balance the equation then the coefficient of each compound or is the number of moles of each compound. I thought this worked for elements and ions as well. So using that logic in the given problem there are 2mo, H3PO4 and then you would convert 2mol H 3PO4 to grams, therefore the numbers in the description of the problem(norpt the equation is not necessary.
1 Answer
- Roger the MoleLv 78 years agoFavorite Answer
There are two different places where moles come into play.
The first is within a balanced equation. Using your example, the balanced equation is:
2 H3PO4 + 3 Ca(OH)2 → Ca3(PO4)2 + 6 H2O
What this says, in theory, is: Every two moles of phosphoric acid react with three moles of calcium hydroxide to produce one mole of calcium phosphate and six moles of water. (Notice that the balanced equation by itself tells you nothing about how much of anything you actually have.)
The second place where moles matter is when you are working stoichiometry problems and you are told how much of something reacts or is produced. If you are not given that amount in moles, you must convert it to moles before you can use it for any calculations. In the present problem, for example:
(0.750 L) x (6.00 mol/L) = 4.50 mol H3PO4
(You do NOT have "2mo, H3PO4". Those two moles are theoretical. What you actually have is 4.50 mol H3PO4.)
Then you can continue the calculation:
(4.50 mol H3PO4) x (1 mol Ca3(PO4)2 / 2 mol H3PO4) = 2.25 mol Ca3(PO4)2
and
(4.50 mol H3PO4) x (6 mol H2O / 2 mol H3PO4) = 13.5 mol H2O
(Notice that the ratios 1 / 2 and 6 / 2 came from the balanced equation.)
Now since the question asks for the mass of products, you convert these moles of products into grams by multiplying by their respective molar masses:
(2.25 mol Ca3(PO4)2) x (310.1782 g Ca3(PO4)2/mol) = 698 g Ca3(PO4)2
(13.5 mol H2O) x (18.01532 g H2O/mol) = 243 g H2O
The important point is: The balanced chemical equation only shows you the theoretical molar ratios. The balanced equation does not tell how much of anything you have or can produce.
