/0's Chem Questions

[jules]

For amino acids, at ph 7, for something such as aspartic acid which has two carboxyl groups, do they both donate hydrogen ions at ph 7? 
I know in ph's above 7 they both donate hydrogen ions but what about at ph 7 when it is a zwitterion?
cheers
good luck for later!

[dekoyl]

When they're zwitterions, haven't they already lost the hydrogen ions from the -COOH functional group?

[linny]

so wait, at ph 7, do we leave the ions neutral or do we add one to the NH2 and take one from the COOH?

[/0]

NaOCl is completely dissociated in water to form and . In solution, hydrolyses according to the equation

100mL of pure water at constant temperature is added to a 100 mL solution of 0.10M NaOCl. When the solution reaches equilibrium,
A.   The has decreased.
B.   The pH of the solution has decreased.
C.   The concentration of has increased.
D.   The value of the equilibrium constant has halved.

I get why the concentration decreases, but how does lead to a decrease in pH? Where does come into it?

[TrueTears]

NaOCl is completely dissociated in water to form and . In solution, hydrolyses according to the equation

100mL of pure water at constant temperature is added to a 100 mL solution of 0.10M NaOCl. When the solution reaches equilibrium,
A.   The has decreased.
B.   The pH of the solution has decreased.
C.   The concentration of has increased.
D.   The value of the equilibrium constant has halved.

I get why the concentration decreases, but how does lead to a decrease in pH? Where does come into it?

Wait... if you add more water shouldn't the concentration of increase?

[dummy]

more [OH-] = more basic = higher PH ...

[mark_alec]

Wait... if you add more water shouldn't the concentration of increase?

The volume is doubled. You don't expect the number of moles of OH- to more than double do you?

As to why pH decreases, [OH-] decreases, and  pH + pOH = 14.

[/0]

Wait... if you add more water shouldn't the concentration of increase?

The volume is doubled. You don't expect the number of moles of OH- to more than double do you?

As to why pH decreases, [OH-] decreases, and  pH + pOH = 14.

ok thanks, I didn't fully understand how pH worked until I learned equilibrium constants, now I think I do

[/0]

Water and chlorine, each at 1atm pressure, are placed in a closed container at 375K, the following reaction occurs.

, at

Which one of the following will be correct at equilibrium at this temperature?
A.
B.
C.
D.

We went through this in class and... I understand how to find the answer by elimination, but I don't fully understand how the answer works and how it can apply to all possible concentrations. thankx


Also another:

. at

In a particular exercise, a mixture of 4.0 mol of sulfur dioxide and 1.0 mol of oxygen is allowed to reach equilibrium at 600K.

The amount of sulfur trioxide present at equilibrium would be
A. 5 mol
B. 4 mol
C. 2 mol
D. less than 2 mol

[/0]

Indigestion is caused by too much hydrochloric acid in the stomach. To ease the pain caused, a tablet can be taken that reacts to reduce the amount of acid present. Which substance would be inappropriate for a manufacturer to include as a major reactant in the tablet?
A.
B.
C.
D.

[monokekie]

Since the equilibrium constant value is very small, the reactions at equilibrum must favour the formation of products to a very small extent. Hence there should be less HCl andO2 present, and more water and chlorine. so... i just guessed its B for some mole ratio reason which i suck @ explaining ....-_-

Water and chlorine, each at 1atm pressure, are placed in a closed container at 375K, the following reaction occurs.

, at

Which one of the following will be correct at equilibrium at this temperature?
A.
B.
C.
D.

We went through this in class and... I understand how to find the answer by elimination, but I don't fully understand how the answer works and how it can apply to all possible concentrations. thankx

i hope you can understand what i just typed.. lol

[lukeperry91]

the answer is D; the oxygen is the limiting reagent, so the maximum sulfur trioxide yield is 2 mol, so :. A&B are cancelled out. To determine whether or not it is C, the K value is taken into account, and it would have to be infinity if n(SO3) was 2 as then n(O2) would be zero, and as the denominator this would make K infinity.. which it isn't, therefore the yield has to be less than two

coblin my tutor helped me with this after it also gave me trouble!

edit: this is for the 2nd latest question

[lukeperry91]

As for the antacid question, ask yourself what sort of qualities would be important when administering a chemical into a person... NaOH is hygroscopic and readily absorbs water from the atmosphere.. it is not usable as a primary standard. The rest will only react with the acid whereas NaOH will react with the atmosphere. Please correct me if im wrong =]

[/0]

Lol thanks so much monokekie and lukeperry91!
@ monokekie: I think now i understand the ratio of concentration is like ratio of moles

[lukeperry91]

As a food additive magnesium carbonate is known as E504, for which the only known side effect is that it may work as a laxative in high concentrations. [4]

Calcium carbonate is widely used medicinally as an inexpensive dietary calcium supplement or antacid.[7]

Magnesium hydroxide, in the form of Milk of Magnesia, is used as an antacid to neutralize stomach acid, and a laxative.

With more reference to unit 4.... "odium hydroxide is completely ionic, containing sodium cations and hydroxide anions. The hydroxide anion makes sodium hydroxide a strong base which reacts with acids to form water and the corresponding salts, e.g., with hydrochloric acid, sodium chloride is formed:

    NaOH(aq) + HCl(aq) → NaCl(aq) + H2O(l)

In general such neutralization reactions are represented by one simple net ionic equation:

    OH−(aq) + H3O+(aq) → 2H2O

This type of reaction with a strong acid, releases heat, and hence is referred to as exothermic."

NaOH + HCl releases alot of heat!!! and that would be a health hazard if it were to be ingested into somones stomache