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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: Alex koosha on January 30, 2016, 10:14:54 AM

Title: How much gram of sorbitol, should I to weigh on the balance?
Post by: Alex koosha on January 30, 2016, 10:14:54 AM

I have 4.6 gram of starch and I want to add 30 % of sorbitol to xylan. How much gram of sorbitol, should I weigh on the balance?

Title: Re: How much gram of sorbitol, should I to weigh on the balance?
Post by: Hunter2 on January 30, 2016, 02:20:20 PM

4,6 g  = 100%. How much is now 30%

Title: Re: How much gram of sorbitol, should I to weigh on the balance?
Post by: Alex koosha on January 30, 2016, 05:05:12 PM

Is 1.96 gram of sorbitol needed correct?

Title: Re: How much gram of sorbitol, should I to weigh on the balance?
Post by: AWK on January 30, 2016, 05:29:15 PM

starch ≠ xylan
?

Title: Re: How much gram of sorbitol, should I to weigh on the balance?
Post by: Alex koosha on January 30, 2016, 05:41:37 PM

Sorry I meant starch not xylan.

Title: Re: How much gram of sorbitol, should I to weigh on the balance?
Post by: billnotgatez on January 30, 2016, 06:15:43 PM

As a side question
Are you actually measuring out the stuff or is this theoretical?

Title: Re: How much gram of sorbitol, should I to weigh on the balance?
Post by: Hunter2 on January 30, 2016, 07:00:31 PM

Quote from: Cyrus the great on January 30, 2016, 05:05:12 PM

Is 1.96 gram of sorbitol needed correct?

How do you calculate that?

Title: Re: How much gram of sorbitol, should I to weigh on the balance?
Post by: Alex koosha on January 31, 2016, 03:21:49 AM

I want sorbitol to be 30% of the total amount. So if I have 70 % starch I have 4.6 g and if I want to have 100 % then how much starch it would be which becomes 6.5.

X=4.6*100/70= 6.50
 
Then I deducted 6.5 from 4.6 which it becomes 6.5-4.6=1.96 gram of sorbitol should be added to the starch.

Title: Re: How much gram of sorbitol, should I to weigh on the balance?
Post by: billnotgatez on January 31, 2016, 04:04:28 AM

Quote from: Cyrus the great on January 31, 2016, 03:21:49 AM

...
X=4.6*100/70= 6.50
...

Why 6.50 and not 6.57?

Title: Re: How much gram of sorbitol, should I to weigh on the balance?
Post by: Alex koosha on January 31, 2016, 04:47:18 AM

Sorry 6.57 and then 1.97 gram of sorbitol.

Is my calculation sounded logical to you?

Title: Re: How much gram of sorbitol, should I to weigh on the balance?
Post by: AWK on January 31, 2016, 06:20:49 AM

Every calculation can be checked, in this case using definition of percentage.

Title: Re: How much gram of sorbitol, should I to weigh on the balance?
Post by: Hunter2 on January 31, 2016, 07:51:07 AM

Quote from: Cyrus the great on January 31, 2016, 04:47:18 AM

Sorry 6.57 and then 1.97 gram of sorbitol.

Is my calculation sounded logical to you?

In the beginning you said you have 4,6 g Starch and want to add 30% of Sorbitol.

In this case its 4,6 g * 0,3 = 1,38 g, what you had to add.

Title: Re: How much gram of sorbitol, should I to weigh on the balance?
Post by: AWK on January 31, 2016, 11:01:42 AM

Which one?

Quote

I have 4.6 gram of starch and I want to add 30 % of sorbitol

Quote

I want sorbitol to be 30% of the total amount.

These are two different problems and two different answers!

Title: Re: How much gram of sorbitol, should I to weigh on the balance?
Post by: Alex koosha on January 31, 2016, 12:32:41 PM

Thank you for your reply. I meant the 2nd one. I want sorbitol to be 30% of the total amount. So,  what is the correct answer?

Title: Re: How much gram of sorbitol, should I to weigh on the balance?
Post by: AWK on January 31, 2016, 12:35:23 PM

Simply checking

Title: Re: How much gram of sorbitol, should I to weigh on the balance?
Post by: Alex koosha on January 31, 2016, 01:24:22 PM

What did you mean. I didnt get it  :)

Title: Re: How much gram of sorbitol, should I to weigh on the balance?
Post by: Alex koosha on January 31, 2016, 01:25:14 PM

Is 1.97 gram of sorbitol correct?

Title: Re: How much gram of sorbitol, should I to weigh on the balance?
Post by: Hunter2 on January 31, 2016, 01:28:12 PM

Yes it is.

Title: Re: How much gram of sorbitol, should I to weigh on the balance?
Post by: Alex koosha on January 31, 2016, 02:51:29 PM

Thank you

Title: Re: How much gram of sorbitol, should I to weigh on the balance?
Post by: billnotgatez on February 01, 2016, 12:48:37 AM

Since the thread has come to an end, I thought I could pose some thoughts without hijacking.
Sometimes I think too much!
When I did this problem my result was
1.9714285714285714285714285714286
(well, that is as far as my calculator went).
Now the only value we had as a given not including the percents was 4.6 grams.
So I assumed that my value needed to be rounded.
What I am not sure of is what the current Pedagogy or practice suggests as the level of rounding.
Is it 2.0 or 1.97 or 1.971 or 1.9714.

The triple beam balance I use goes to 0.1 grams.
I could only measure 2.0 grams as the closest value.
That level of rounding would match the original base number as 4.6.
I also use a digital scale that goes to 0.01 grams.
I could then measure 1.97 grams.
But would the original base number have been noted as 4.60?
And lastly I know there are scales that measure to 0.0001 grams.
So I could measure 1.9714 grams.
But then would the original base number be 4.6000?

My friend just called me pedantic for even thinking about this problem.

I know I knew the answer to this at sometime but can not articulate it - so I mention it here.

Title: Re: How much gram of sorbitol, should I to weigh on the balance?
Post by: Borek on February 01, 2016, 03:47:05 AM

Both numbers from the opening post have 2 significant digits, so 2.0 seems a reasonable rounding.