ATAR Notes: Forum
VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Chemistry => Topic started by: johnsmith123 on March 11, 2014, 06:32:58 pm
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Sorry guys I know this may be obvious but I am unsure.
When determining how many S.F to make answer to is the number of S.F in the molar mass taken into consideration.
For instance if the information was: Mass=0.1234g Molar Mass = 96.1g/mol
The would answer for number of moles would be to 3 S.F?
Thanks.
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From my experience the number of significant figures isn't an issue, but rather the number of decimal places. In general terms, two decimal places is perfectly fine, however I've been told to always go as many as there in the number in the question with the most amount of decimal places. Therefore, in your example, it would be 4 decimal places.
The reason I said decimal and not significant figures is due to the following.
Answer = 0.000000043291
You wouldn't write 0.0000000433
But rather, you'd write (assuming this is to 3 decimal places), 4.329x10^(-8)
Hope that helps!! :D
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From my experience the number of significant figures isn't an issue, but rather the number of decimal places. In general terms, two decimal places is perfectly fine, however I've been told to always go as many as there in the number in the question with the most amount of decimal places. Therefore, in your example, it would be 4 decimal places.
The reason I said decimal and not significant figures is due to the following.
Answer = 0.000000043291
You wouldn't write 0.0000000433
But rather, you'd write (assuming this is to 3 decimal places), 4.329x10^(-8)
Hope that helps!! :D
Unfortunately this isn't correct for VCE Chemistry. You need to give your answer to the appropriate number of significant figures in strict accordance with the conventions
Sorry guys I know this may be obvious but I am unsure.
When determining how many S.F to make answer to is the number of S.F in the molar mass taken into consideration.
For instance if the information was: Mass=0.1234g Molar Mass = 96.1g/mol
The would answer for number of moles would be to 3 S.F?
Thanks.
Yes the number of significant figures given for any molar masses used must be taken into account and yes what you've done in your example is correct. Note, however that when *adding* two numbers, you give you answer to the least number of *decimal places* not significant figures. So, for example, if you were told that M(H) = 1.0 g/mol and M(C) = 12.0 g/mol, then you would say that M(CH4) = 16.0 g/mol not 16 g/mol.
Hope that helps! =)
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Unfortunately this isn't correct for VCE Chemistry. You need to give your answer to the appropriate number of significant figures in strict accordance with the conventions
Yes the number of significant figures given for any molar masses used must be taken into account and yes what you've done in your example is correct. Note, however that when *adding* two numbers, you give you answer to the least number of *decimal places* not significant figures. So, for example, if you were told that M(H) = 1.0 g/mol and M(C) = 12.0 g/mol, then you would say that M(CH4) = 16.0 g/mol not 16 g/mol.
Hope that helps! =)
How about for multiplying and dividing? Is it the least number of sf of the most fro the question? Different teachers have been saying different things..
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Great thanks guys
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How about for multiplying and dividing? Is it the least number of sf of the most fro the question? Different teachers have been saying different things..
Least number. Think about it rationally - the more significant figures you state, the more certain you're saying you are about your answer. Suppose I have some really accurately determined empirical quantity, 1.252463231999124, and I multiply it by some much less accurately determined quantity, 4.3. Now, I'm hardly going to be entitled to say that I know the product of these two quantities to the same degree of certainty that I knew the really accurately determined one... I'm only going to know it to the level of certainly of the quantity that I'm least sure about.
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Least number. Think about it rationally - the more significant figures you state, the more certain you're saying you are about your answer. Suppose I have some really accurately determined empirical quantity, 1.252463231999124, and I multiply it by some much less accurately determined quantity, 4.3. Now, I'm hardly going to be entitled to say that I know the product of these two quantities to the same degree of certainty that I knew the really accurately determined one... I'm only going to know it to the level of certainly of the quantity that I'm least sure about.
Thank you, that makes sense :)