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Positronix

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- percentage of elements in a compound without involving molarity?

Thanks in advance for explaining this to me.

I have a very small sample of thorium dioxide in a sealed ampoule (reasonably pure) as an example of thorium for a display.

Every time I wonder what % of the compound is thorium people start talking moles and grams and envisioning it in a solution...

That's great to be able to do all that, and I'll re-acquaint myself with it (I used to do the equations back in college and forgot)

but right off the top of one's head:

Why can't I just say:

the formula for the compound is Th02

1 thorium and 2 oxygens

On the periodic table:

thorium has a mass of 90

oxygen has a mass of 8 (and there's two, so we'll say 8*2=16)

90 / 16 = 5.625

therefore there is 5.625 times as much Th as there is O in ThO2

for %, 100 / 5.625 = 17.778 % Oxygen

100 - 17.778= 82.222% Thorium

and if this is correct, why do I even have to get into molarity for dry weight?

If I have 1 gram of ThO2 why can't I just use the above to say it contains .822 g of Th?

Thanks again.

I have a very small sample of thorium dioxide in a sealed ampoule (reasonably pure) as an example of thorium for a display.

Every time I wonder what % of the compound is thorium people start talking moles and grams and envisioning it in a solution...

That's great to be able to do all that, and I'll re-acquaint myself with it (I used to do the equations back in college and forgot)

but right off the top of one's head:

Why can't I just say:

the formula for the compound is Th02

1 thorium and 2 oxygens

On the periodic table:

thorium has a mass of 90

oxygen has a mass of 8 (and there's two, so we'll say 8*2=16)

90 / 16 = 5.625

therefore there is 5.625 times as much Th as there is O in ThO2

for %, 100 / 5.625 = 17.778 % Oxygen

100 - 17.778= 82.222% Thorium

and if this is correct, why do I even have to get into molarity for dry weight?

If I have 1 gram of ThO2 why can't I just use the above to say it contains .822 g of Th?

Thanks again.