Clarification on the Vitamin C Example

[Sunia Akaveka 4I]

In the example given in class regarding 8.00g of Vitamin C, where the carbon amounted to 3.27g, hydrogen amounted to 0.366g, and oxygen was 4.36g, Dr. Lavelle emphasized the importance of double-checking that the sum of these amounts equal to the 8.00g. When adding these, you receive a total of 7.996g. What happens to the 0.004g that is allegedly accounted for?

[andrewcj 2C]

My best guess would be that rounding caused the masses of the individual elements to be a little smaller than they really are, which creates a small discrepancy in the summed mass and the total mass. In real life, our instruments are not always perfect, and this might be trying to show that.

[Ryan 1K]

Elaborating on the rounding aspect, all the numbers provided have three significant figures. Since one of the numbers is less than 1, it makes sense for there to be some small mass lost in the calculations as the other numbers would be rounded.

[Rishika Yadav 3D]

I think the small amount 'lost' is due to rounding - if we went out further in the decimal places then we would likely have gotten a value slightly closer to 8.000. Additionally, in real life we will nearly always be slightly off of the theoretical value, due to things like solution sticking to the beaker or other instruments, weighing issues, etc.

[Sunia Akaveka 4I]

So, if this 0.004g is lost to discrepancy or for rounding purposes, wouldn’t this further our mass percentage composition data from accuracy? Would this be more considered precision?

[Katie Bart 1I]

It would, but we have to make sure we account for significant figures. Also, we lose precision every time we round so this isn't significantly worse than other problems we have done.

[504939134]

I believe this was because we are supposed to round up.