[DesertRose]

Hi, my question is this; how do you convert grams to molecules??
i have a question based on this and what i did was i converted the grams to moles first and then from moles to molecules. however the answer i got was negative answer (which means that it is wrong).
i tried the question a couple times well and i still can't tell where i am going wrong.
Could someone guide me through the process please??
Any help would be greatly appreciated!!
thank you!

[yeliel87]

That's correct. You convert from grams to moles by dividing the number of grams by the value in the periodic table for that element then you multiply the answer by avogadro's number which is 6.022*10^23. If you post the problem you're working on, I may be able to see what you're doing incorrectly.

[Borek]

I guess you keyed it wrong into your calculator. Please elaborate on how you calculated the result.

[DesertRose]

Hi, the question is this;

convert 0.35g BaOH to molecules.
so what i did was, i said the RMM of BaOH is 154g and i refered to the number of moles as 'x'.
after, i wrote;

RMM + x = g
154 + x = .35g
        x = .35 - 154
          = -153.7 moles
          = - 9.222 * 10^25  (which is wrong)

i decided to use a different method, and this is what i got;

154g BaOH =6*10^23
        .35g = x
(i cross multiplied and got....)
             = 1.36 * 10^21

So is any method correct??
thank you!

[cliverlong]

I would approach this way

Moles = mass / Mr

moles BaOH = 0.35 g / 154 g mol^-1 = 0.0023 moles

Molecules = moles x 6 x 10²³

molecules = 0.0023 x  6 x 10²³ = 1.36 x 10²¹

Clive

[DesertRose]

thank you soo much guys!!!

[Borek]

Hi, the question is this;

convert 0.35g BaOH to molecules.

No, question was "barium hydroxide" and barium hydroxide is NOT BaOH.

so what i did was, i said the RMM of BaOH is 154g and i refered to the number of moles as 'x'.

RMM of barium hydroxide is not 154 g.

RMM + x = g

This is completely wrong. You are adding number of moles to molar mass in hope the result will be mass of the sample? It is about as correct as adding shoe number to monthly income to find out age.

Ah, I think I know what you did. You misread your notes or your textbook, where it was stated that mass of the substance is number of moles TIMES molar mass.

i decided to use a different method, and this is what i got;

154g BaOH =6*10^23
        .35g = x
(i cross multiplied and got....)
             = 1.36 * 10^21

This is much closer, but still wrong - 154 g/mol is not a correct value.

[DesertRose]

It wasn't 154g/mol. It was to convert the .35g to molecules. The RMM i have for BaOH (given by my teacher) is 154g. So i worked it out using this value and i got (as my answer) 1.36 * 10^23.
I also have ( BaOH) as barium hydroxide (also given by my teacher).

[Borek]

Either you misunderstood something or you teacher should not teach chemistry. RMM you have for barium hydroxide is wrong and barium hydroxide formula is not BaOH. You can repeat these things hundred times, but they won't get correct.

It wasn't 154g/mol. It was to convert the .35g to molecules.

Sorry, but what you wrote makes no sense. It wasn't 154, but RMM you were given was 154?

[DesertRose]

yes. but could you explain to me how is it that that isn't the correct answer please?

[Borek]

I have no idea what you refer to at the moment. Please be precise, as the only thing you can get from chaos is more chaos.

[DesertRose]

"RMM you have for barium hydroxide is wrong and barium hydroxide formula is not BaOH. You can repeat these things hundred times, but they won't get correct."

[Borek]

http://lmgtfy.com/?q=barium+hydroxide