Physical Chemistry Answers

Hello,

Can you please explaine to me what's a "quantum size-effect" ?

If a water electrolysis cell operates at a current of 7.7A. how long will it take to generate 25.0L of hydrogen gas at a pressure of 27.0 atm
and a temperature of 25 degrees celcius

A mixture of ZnCl2 and CdCl2 weighs 1.000 g.
Treatment with AgNO3(aq) converts all of the
chloride into 1.902 g of AgCl. What is the percent
by mass of ZnCl2 in the original mixture? (Choose
the closest value.)
A 15.0%
B 50.0%
C 53.9%
D 62.6%
E 84.1%

What are the two different types of molecules? Write examples for each type.

66.
Determine the mass of a nonvolatile, nonionizing compound that must be added to 3.81 kg of water to lower the freezing point to 98.70°C. The molar mass of the compound is 50.0 g/mol and the Kf for water is 1.86°C kg/mol.
A.
202 g
B.
133 g
C.
461 g
D.
9.17 g
E.
18.8 g

dear sir
I HAVE A QUESTION ABOUT GAS CHROMATOGRAPHY.WHEN WE USE CONSTANT PRESSURE OR CONSTANT FLOW FOR COLUMN OR IN MAKE METHOD FOR ANALYSIS?
BEST REGARDS
TONE

why is it useful to use moles to measure chemical quantities

dear sir
I HAVE A QUESTION ABOUT GAS CHROMATOGRAPHY.WHEN WE USE CONSTANT PRESSURE OR CONSTANT FLOW FOR COLUMN OR IN MAKE METHOD FOR ANALYSIS?
BEST REGARDS
TONE

Hi, I have some samples with a volume about 2ml kept in -80 ready to ship for the NMR analysis. They contain some chemicals such as pyruvate, Malate, ATP, succinate,etc. I have forgotten to add 0.3mM creatinine which is used as a standard. As I haven't sent them yet, I wonder if i still can add the creatinine into my samples without thawing them. Because I just feel if I defrost my samples, some chemicals might get damaged. I would appreciate if could help me with this issue as soon as possible. Thanks