For a chemistry project, I made simple beer out of malted grains that I heated then cooled.

I want to measure the sugar content of my beer with Fehling titration.

Different types of sugars can be found in beer, such as glucose and maltose, which contain an aldehyde (RCHO) group, therefore the Fehling test can be used.

The sugar will reduce the ions Cu

RCOH

I calculated the %m/m of glucose in rye, based on USDA's data, so there's around 0,98% of glucose in rye.

I used 75 g of rye, which sums up to around 0,735 g of glucose.

I then calculated the molarity of glucose, where the volume was 0,46 L, which gave me 0,008869 M of glucose.

After that, I am not too sure how to proceed with the titration. I searched for determination of glucose/reducing sugars by Fehling titration and found some procedures, such as:

http://corn.org/wp-content/uploads/2009/12/DEXTR.02.pdf

https://www.york.ac.uk/org/seg/salters/ChemistryArchive/ResourceSheets/sugars.PDF

http://blamp.sites.truman.edu/files/2016/01/Fehling-final.pdf

So I plan on using Dextrose (D-Glucose) Anhydrous as well.

And I am rather lost, is there a way to determine what quantities of the sample, the Fehling solutions, the amount of distilled water, the mass of dextrose, etc. that I will need to use?

Do I just pick a certain volume of the rye sample solution on my own and then try to find quantities of the other substances from it? If so, how can I proceed to do that?

I apologize for the long post.

Any help is appreciated. Thank you very much!]]>

Consider the following reaction:

C2H4(g)+H2(g)→C2H6(g)

ΔH=−137.5 kJ; ΔS=−120.5 J/K

Calculate ΔG at 25∘C and determine whether the reaction is spontaneous.

Express the free energy change in joules to four significant figures.

Here, I got 256.2 kJ but this is incorrect and I'm not sure what I did wrong after checking my work.

Question 2:

At 25 ∘C the reaction from Part A has a composition as shown in the table below.

Substance Pressure

(atm)

C2H2(g) 4.15

H2(g) 5.35

C2H6(g) 2.25×10−2

What is the free energy change, ΔG, in kilojoules for the reaction under these conditions?

Express your answer numerically in kilojoules.

I have been given T = 298 K and Delta G = -242.1kJ. And I have also been given the formula,

which is Delta G = dG + RT ln Q.

My original Delta G that I calculated was 1016 J. However, this is wrong and I'm not sure where I went wrong.

Thank you, no matter how I do both calculations I keep getting the wrong answer.]]>

E.g., benzene may be nominally D2h symmetry - with electronic states having symmetries derived from the D2h character table - but the nuclei aren't stationary. During a vibration, the symmetry changes. If there is a certain vibration that can cause the ground and electronic states to temporarily have the same overall symmetry classification, coupling of the states becomes possible. Vibronic coupling is one reason why spectroscopic transitions can often occur between electronic states that have seemingly incompatible symmetries - the transition occurs through a vibrational mode the satisfies the symmetry requirement for the selection rule. Similar vibronic effects can also have an effect on whether avoided crossings and noncrossing impacts excited-state relaxation processes. ]]>