Wow i really neeed help solving chemistry problem?

Question

15g magnesium reacts with 30g of calcium phosphate

how many moles of magnesium phosphate are produced?

how many grams of magnesium phosphate are produced.

3Mg+ Ca3(PO4)2->Mg3(PO4)2+ 3 Ca(balanced)

can you please tell me the steps? i took notes but they are confusing....:(

Answer 1

First you need the balanced equation which you have got.

Second you need to work out the moles of the reactants.
moles = mass/ MW
so;
Moles Mg = 15/24.3
= 0.617

Moles Ca3(PO4)2 = 30/ (40*3 + (31+16*4)*2)
= 0.097

Third: Find out the limiting reagent
3 moles of Mg react with 1 mole of Ca3(PO4)2. For 0.097 moles of Ca3(PO4)2 you require 0.291 moles of Mg. So their is an excess of Mg or put another way the limiting reagent is the Calcium Phosphate.

Fourth: Work out the number of moles of Mg3(PO4)2.
As it is a 1:1 mole relationship between the formation of Mg3(PO4)2 and Ca3(PO4)2.
Moles Mg3(PO4)2 = moles Ca3(PO4)2
=0.097
grams Mg3(PO4)2 = moles Mg3(PO4)2 * MW
=0.097 * (24.3*3 + (31+16*4)*2)
=25g

Answer 2

You need to find the limiting reagant, that is, the reactant that will run out first. First convert 15g Mg into moles, 3mol Mg converted to 1mol Mg3(PO4)2 . To save time, don't convert into grams, just yet. Instead, do the same thing with 30g of Ca3(PO4)2 , converting grams to moles and moles of Ca... to moles of Mg... (too lazy to write formula) The one with the least amount of moles is the limiting reagent, and the amount of Mg... you have is the answer, in moles. Now, convert into grams to get your final answer.

Answer 3

This is stoichiometry

Convert the 15 g of Mg to moles

Multiply by the molar ratio to get moles of Mag. Phos.

Multiply by the MM of Mg Phos to get grams

Answer 4

Actually this is a limiting reagent problem.

First you must convert each of your given reactants into moles:

15 g Mg x [1 mol / 24.3 g] = 0.62 mol Mg

30 g Calc. phos. [ 1 mol / 310 g] = 0.1 mol calc. phos.

now you must see how much of the magnesium phosphate each of the reactants would allow you to produce. you use the coefficients in the balanced equation to set up your conversion factors:

0.62 mol Mg x [ 1 mol mag phos / 3 mol Mg ] = 0.21 mol mag phos.

0.1 mol calc. phos. x [ 1 mol mag phos / 1 mol calc phos ] = 0.1 mol mag phos.

since the calcium phosphate is allowing you to produce the *least* amount of product (0.1 mol), the calcium phosphate is the limiting reagent and you will produce 0.1 mol of magnesium phosphate.

you can then convert the 0.1 mol of magnesium phosphate into grams:

0.1 mol mag phos x [ 263 g mag phos / 1 mol mag phos. ] = 26.3 g mag. phos.

Answer 5

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