How did you get 9.5%9.5% for the theoretical yield of the potato chips in the Food Calorimetry Lab? I get 11%11%.
1 Answer
Referring to this video:
It is a difference of rounding. If you do the actual earlier calculations and keep enough decimal places, you'll be starting with:
"34 g"34 g of potato chips in one serving"9.6 calories"9.6 calories in one potato chip"1.75 g"1.75 g for each potato chip on average
Therefore, the calories per gram of potato chip is about:
"9.6 Cal"/"1.75 g" = 5.4_(86)" Cal/g"9.6 Cal1.75 g=5.486 Cal/g
where a subscript indicates the uncertain digits in our significant figures. This is actually where you should start noting that it's not precisely
On the food label Tyler gives, we see the
(34 cancel"g")/"serving" xx (5.4_(86)" Cal")/cancel"g" = 1.8_(651)xx10^2 "Cal/serving"
which rounds to
"% Error" = |"Actual" - "Theoretical"|/("Theoretical") xx 100% (His "actual" is actually our "theoretical", and his "measured" is our "actual")
= |190 - 210|/(210)xx100% = color(red)(9.5%) if you use190 .
= color(blue)(11._(19)%) if you use"186.51 Cal" and then round.
Tyler wasn't wrong; he was just (implicitly?) saving all his digits in his calculator and rounding to the right significant figures for his audience.
So always save your rounding until the end to avoid differences like this.