Thursday, November 11, 2010

Chem Mid-Term Reveiw

2.The following length measurements were taken by students using several different measuring devices. Find the average of the measurements. Make sure that your answer has the correct number of sig figs. 10.05 cm, 10.1 cm,9.741cm, 10.6 cm, 10.5 cm. If the actual length were known to be 10.00, what would the percent error be?(Again be mindful of sig figs).

10.05 + 10.1 + 9.741 + 10.6 + 10.9 = 50.991 = 51.0

51.0 / 5 = 10. 2

(A.V. - E.V.) / A.V. x 100

(10 - 10.2) / 10 x 100

.2 / 10 x 100 

.02 x 100 


*** To find the percent error the parenthesis should really be absolute value bars.


  1. congrats Emily on getting the right answer. you're so good at chemistry I aspire to be like you. there isn't much to add but if I were to add something it would probably just be showing all the actual sig fig rounding and explain a little bit on how you decided to round (even though I'm sure we know) but good job!

  2. Emily, I got the same number as you! You did all the steps correctly, but you could have added a little explanation why you did each step. I think you could have explained why you rounded to so many decimal places(sig figs) and written to the side what A.V. and E.V. stand for. You could have also explained that in the first two steps you were finding the average of the measurements. I like how you put the answer in red. Great job!

  3. Emily!! awesome job!! i thing you did very well and you did the correct amount of sig figs. a little explanation for the steps would have been a bit helpful, but it was pretty self explanatory and you did an awesome job!!

  4. Emily, you did an awesome job! It was very easy to follow and I had the same answer! However, if i didn't know how to approach this problem, a little more explanation would have helped. Also you a tool like math-type would I have taken care of the absolute value signs, but i know how much of a pain that is. Overall great job!!

  5. Good job Emily! I got the same thing as you and it was pretty easy to follow! Next time, i think you should maybe number your steps because at the end it may have been hard for someone who didn't understand this problem in the first place to know that they needed to multiply by 100. Otherwise- great work!