## anonymous one year ago When I have something like: Al(OH)3 would I set it up like this: 26.982(15.999+1.008)*3?

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1. hwyl

what are you trying to do?

2. anonymous

mole to grams conversions the question is: How many moles are in 98.3 grams of aluminum hydroxide, Al(OH)3

3. hwyl

ah

4. hwyl

how many moles of $$\sf Al(OH)_3$$ do you have?

5. anonymous

thats the question; it only gave grams for me to find that.

6. hwyl

you only have one mole

7. hwyl

if you do not see a number before the name of the compound or molecule then it means there is only one mole.

8. hwyl

$$\sf \huge x~ mole_{Al(OH)_3} \times \frac{grams_{Al(OH)_3}}{1 ~ mole_{Al(OH)_3}} =$$

9. hwyl

do you see how the mole unit for a particular thing is canceled out algebraically?

10. hwyl

$$\large a \times \huge \frac{b}{a} = b$$

11. anonymous

yeah I see where it would be cancelled out. I just need to know how to find the molecular weight of the aluminum hydroxide.

12. hwyl

whatever unit you're trying to convert out of, you need to divide by itself

13. hwyl

molecular weight follows the conservation of mass so if you see Al it means there is 1 Al in there if you see $$\sf (OH)_3$$ it means that there are 3 O's and 3 H's; the subscripts tell you how many there are for whatever each element that is enclosed in parenthesis

14. hwyl

usually when there's 1, we do not write it out. it is just like saying a mole of something - it is implicit that the word "a" denotes 1

15. hwyl

you're going to add all the weights of each elements in that molecule/compound

16. hwyl

$$\sf \large Al(OH)_3 = [1 \times (weight_{Al})] + [3 \times (weight_{O}+weight_{H})]$$

17. hwyl

get it?

18. anonymous

so the answer is 78.003 correct?

19. hwyl

I don't know the individual atomic mass units of each elements, that is something you need to reference to a periodic table.

20. anonymous

its in the top

21. hwyl

22. anonymous

okay well thank you so much for you're help!!

23. anonymous

@hwyl what about when it says: Ca3(PO3)2

24. hwyl

Ca: $$3 \times \sf Ca$$ P: $$2 \times \sf P$$ O: $$2 \times 3 \sf ~ O$$