Question

Would someone mind proofreading this,

Answer 1

Im writing a formal lab report on an experiment of gravimetric analysis, I am writing my abstract and am stuck at these last two sentences. "The purpose of experiment 4 was to determine the chloride content of an unknown soluble chloride sample using gravimetric analysis. Gravimetric analysis is a technique that is based on the quantitative isolation of a desired constituent. This form of analysis involves comparing the masses of two compounds in order to determine the amount of constituent present in an unknown sample."

Answer 2

Gravimetric analysis is a technique that is based on the quantitative determination of the mass of an analyte. Maybe I would change it to this, what you have seems pretty accurate.

The last sentence could also potentially be changed from constituent to compound/element or analyte

Answer 3

Actually you should be fine using constituent.

Answer 4

It is important to mention mass when you explain gravimetric analysis because it really is just the determination of mass of a compound in a sample

Answer 5

oh thats great! that sentence sounds much better actually. :) So would you recommend that i leave the last sentence as is?

Answer 6

Tbh I don't really like the last sentence but it is alright maybe change constituent to analyte

Answer 7

doesn't matter though actually

Answer 8

it is fine, I dont see why a teacher/prof would deduct marks for that

Answer 9

or TA

Answer 10

haha, well thank you i appreciate your honesty and help! :) Ill see what i do with it. Starting off is always the most difficult part after i can go back and proofread

Answer 11

Well an abstract you should always write last

Answer 12

if you are doing an abstract I assume you are doing an introduction though

Answer 13

sorry I'm pretty sleep deprived

Answer 14

touche. I am all done with the rest, just have this left!

Answer 15

don't worry about it at least your honest!

Answer 16

What technique did you perform out of interest?

Answer 17

We used gravimetric analysis using vacuum filtration ;p

Answer 18

Oh so you just did a precipitation, then vacuum filtered, put it in a desiccator, then weigh it.

Then just use gravimetric factor and a balanced reaction equation to get back to the original amount of compound present in your sample

Answer 19

how are you comparing the masses of two compounds?

Answer 20

I'm making assumptions though I dont really know what you did in your experiment

Answer 21

yes exactly that! Well to be honest chemistry is not my best subject so for the most part i just wing it :/

Answer 22

So you just used the balanced equation to figure out the original amount of compound present in your solution. So how did you use two masses?

Answer 23

you should really only need to use the mass of precipitate to find the mass of the original compound

Answer 24

If you are referring to gravimetric factor then yeah you use two molecular masses

Answer 25

no we didn't use a balanced equation. basically we found the mass of AgCl used and from there used that mass to determine the amount of Cl in the original sample. & from thereee we calculated the percent of Cl in the unknown sample

Answer 26

So you did a titration

Answer 27

kind of

Answer 28

Sort of. I do have a question though if you mind helping

Answer 29

No problem ask away

Answer 30

At the end of the lab our professor has us calculate an average percent among myself and another two students. What is the purpose of doing that?

Answer 31

What does the average percent show? or tell you? was very confused

Answer 32

Can you show me the formula?

Answer 33

Oh wait one sec

Answer 34

ill show you my calculations but it was basically finding the mean percent

Answer 35

Well when you do an experiment you should always do it at least in triplicate as this gets you close to the real value

Answer 36

so when you take an average percentage you are getting closer to the real percentage

Answer 37

at least I'm speaking in an experimental sense

Answer 38

in terms of that example you gave me it is more of an indicator how a group of people did on an exam, although mean has a problem in that extreme values can throw it off

Answer 39

So just say,

a three people get a 10%, 50% and 51%
So the average is 37%, which I would say is pretty miss representative of the actual values (although this example is not very good, because of the small amount of values, it is like taking the average of a large group of middle class peoples net worth and then also including bill gates net worth, the value you get is going to be way off). I'm going on a tangent though

Answer 40

This is something you should be a aware of as if you get outliers in your experiments you should tell your prof/teacher about it and see if it is possible to ignore

Answer 41

ok I'm done rambling about percentages do you kind of follow?

Answer 42

yes i understand it better. However, in my case all the percents we close to the average value so would that mean the average is a good representation of the data

Answer 43

Well there is precision and accuracy

Answer 44

A high precision is when the values are very close together in this case the precentages, the accuracy you have no idea unless you have a reference to compare to

Answer 45

wellll

Answer 46

I think you used a standard though in your experiment

Answer 47

For my given sample i was given the theoretical value

Answer 48

It would mean you have good precision I think

Answer 49

i calculated the percent of Cl in the unknown sample to be 57.29% & the theoretical value was 57.59 %

Answer 50

precision is hitting the same spot on the dart board, accuracy is hitting the center of the dart board

Answer 51

Where are you getting the theoretical value? Sorry not really sure I completely understand what you did in your experiment not that you need to explain it

Answer 52

hah its ok! Well each student was given an unknown sample #, mine was #53. Once i finished my experiment i calculated the Cl mass in the unknown and the percent of Cl in the sample. In addition my professor gave us each our theoretical values based on which sample number we got

Answer 53

kinda make sense?

Answer 54

Yes it makes loads of sense

Answer 55

You can say that your experiment was successful in identifying the amount of analyte present in the sample relative to the theoretical within (Theoretical % - experimental %)

Answer 56

or something like that

Answer 57

You could say it is close but when you write scientific literature you want to avoid being subjective

Answer 58

When ever comparing two things you need a reference

Answer 59

but again I'm rambling blah

Answer 60

Does that kind of help?

Answer 61

no i totally understand! much better

Answer 62

You can try to rationalize opinions though

Answer 63

one more thing!

Answer 64

If you have other data to show that it is not really an opinion, and more a logical conclusion

Answer 65

If you dont follow that last part dont worry about it.

Answer 66

when you said, "the amount of analyte present in the sample relative to the theoretical within (Theoretical % - experimental %) ". In the parenthesis would that value just be the difference among the two?

Answer 67

ask away I need to go soon need to finish my food and study

Answer 68

yeah you would just show how close the theoretical value is from the experimental,

you could also use percent yield which just shows how close the experimental is to the theoretical yield, but that is more used for synthesis problems

Answer 69

from that the reader could say oh that is close or oh that is far away I dont know

Answer 70

oh sorry synthesis experiments

Answer 71

ahh ok. i understand i think I'm good now :) Thank you so much!

Answer 72

No problem good luck in chemistry and your lab report :)

Answer 73

and on*

Answer 74

thank you so much! :)