So what is the molar mass of glucose? Well to figure that out, and that's why this periodic table of elements is useful, we just have to figure out the molar mass of the constituent elements. Well then we just divide the mass of our sampleīy the mass per mole and we'll know how many moles we have. And so we have a 1.52 kilograms sample of our molecule in question, of glucose so if we can figure out the mass per mole, or another way to think about it, the molar mass of glucose, If I say a mole of something, I'm saying that's Avogadro's If I said a dozen of something, you'd say oh, that's 12 of that thing. Remember, mole is really, you can view it as a Trying to figure out the number of moles, So like always, pause this video and try to figure this out on your own and this periodic table ofĮlements will prove useful. We are asked to calculate the number of moles in a 1.52 So the final answer should be reported as 180.16 g/mol. So the 5 digit get upgraded to a 6 in the answer. Since the number we're discarding (6) is larger than 4 we round the digit it is next to up one number. So we only want the 1 and 5 digits and want to discard the 6. But because we only have two decimals digits for the 72.06 and 96.00 numbers, our answer is limited to two decimal digits. So after multiplying Sal is performing this calculation: 72.06 + 84.156 + 96.00, which mathematically would yield 180.156. For addition the sig fig rule is that we can only have as many decimal digits as do in the calculation number with the lowest number of decimal digits. You should look into sig figs in greater detail, but in this problem Sal is adding three numbers together. And the rules we use to judge how many digits are permissible are significant figures, or sig figs.
But in science we are more conservative with the digits we use because of the precision of our measuring instruments. After a calculation would be able to use all the digits of the final number as our answer if we only wanted a mathematical answer. It's important to keep in mind significant figures are important for doing calculations in a science like chemistry.
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