Question

How many grams of calcium phosphate can be produced when 78.5 grams of calcium hydroxide reacts with excess phosphoric acid?

Unbalanced equation: H3PO4 + Ca(OH)2 ---> H2O + Ca3(PO4)2
@DanJS

Answer 1

try balancing the equation, i will brb in 2 min, have to change over laundry

Answer 2

ok

Answer 3

\(\sf H_3PO_4 + 3Ca(OH)_2 \rightarrow H_2O + Ca_3(PO_4)_2\)
Hmmm I am getting stuck balancing this

Answer 4

Do the cation metals first

Answer 5

then groups likeOH and PO4

Answer 6

then finally oxygen and hydrogen

Answer 7

2,3,6,1 try that

Answer 8

\(\sf \sf 2H_3PO_4 + 3Ca(OH)_2 \rightarrow 6H_2O + Ca_3(PO_4)_2\)

Answer 9

really no trick to doing that, just which atoms are more important to balance first....and you can use fractions if needed, then multiply through at the end to get all whole numbers

Answer 10

It still isn't balanced though. There are 8 H on the left but 12 on the right.

Answer 11

look again...

(OH)2 has 2 H each, and you have 3 molecules, that is 6 H atoms there

Answer 12

H: 6 + 6 = 12

Answer 13

Oh ok

Answer 14

Just have to keep tryin at those, adding coefficients and changing them around until it checks out

Answer 15

doing, metal cations first, then groups(OH) and (PO4) , then oxygen, then hydrogen

Answer 16

So now you have the balanced equation , we can do the stoichiometry

Answer 17

2H3PO4 + 3Ca(OH)2 → 6 H2O + Ca3(PO4)2

78.5g Ca(OH)2
Excess = infinite H3PO4

Answer 18

Calculate the Molar Masses of each compound in question

Answer 19

and i will start drawing up the solution

Answer 20

H3PO4 = 98 g/mol
Ca(OH)2 = 74.093 g/mol
H2O = 18.01528 g/mol
Ca3(PO4)2 = 310.1767 g/mol

Answer 21

I used your molar masses, assuming they are right.. :)

Answer 22

109.54

Answer 23

general format:

(Grams reactant) x (Molar Mass) x (mole Ratio) x ( Molar mass)

Answer 24

yep that is what i got

Answer 25

grams of calcium phosphate

Answer 26

see how the units cancel, and you are left with what you are looking for, grams of calcium phosphate?

Answer 27

Yes

Answer 28

That is all you have to do..

Start by writing what they give you... then multiply by fractions of 1 and end with the unit they are lookig for

Answer 29

if you want 'how many molecules' use as the last fraction this instead
\[\frac{ 6.022 x 10^{23} ~molecules ~~Ca(PO4)2 }{ 1 mol ~~Ca(PO4)2 }\]