9
votes
Why do we say the position of equilibrium is shifted even when K is the same?
Is there any specific definition of position of equilibrium?
No, it is a fuzzy concept and not very helpful. When a reaction is at equilibrium, there is a certain composition of the equilibrium ...
- 39.2k
8
votes
Accepted
Why can't the product of an acid reacting with water react with water itself and produce OH-?
It definitely does. Let's simplify it to a monoprotic acid (like acetic acid, $\ce{CH3COOH}$), which I'll just represent as $\ce{HA}$ for simplicity. In a solution of the acid, you will have all of ...
- 71.1k
8
votes
Accepted
Experimental evidence for zwitterions
That is a very difficult problem worth a PhD project in physical chemistry. Intially, I thought one could try capillary electrophoresis at different pHs and if the analyte travels with the ...
- 39.1k
8
votes
What is the basis for the relationship of Gibbs energy and extent of reaction shown in this graph?
What an interesting question! I was perplexed when I first read this. And then I remembered what my professor told me in college, that is, "when in doubt, read." So, I read and found an ...
- 2,162
8
votes
Accepted
What is the basis for the relationship of Gibbs energy and extent of reaction shown in this graph?
The Gibbs energy for a system at a fixed pressure and temperature, is only a function of the concentration of the species. We write it in a differental form
$$ dG = \sum_j \mu_j dn_j \tag{1} $$
Our ...
- 2,246
7
votes
Can ICE tables give two answers?
Scenarios leading to a quadratic equation have two mathematical solutions, real or complex. But, one of them often does not have interpretation in scientific context, as it's value is out of the ...
- 39.5k
7
votes
Accepted
Effect of inert gas on the rate of reaction
At otherwise the same partial pressure of the reacting gas, an inert gas slows down heterogenous reactions of a gas with condensed phases.
It is caused by local additional decreasing of partial ...
- 39.5k
7
votes
What is the basis for the relationship of Gibbs energy and extent of reaction shown in this graph?
UPDATE: In the comments to this and other answers, the question came up why the Gibbs energy of mixing is related to chemical reactions. In a chemical reaction, reactant turns into product (or vice ...
- 39.2k
7
votes
Accepted
How does enzyme velocity decrease as reaction quotient approaches equilibrium constant?
The Michaelis-Menten mechanism is the following:
\begin{align}
\ce{E + S &<-->[$k_1$][$k_{-1}$] ES} \tag{R1} \\
\ce{ES &->[$k_2$] P + E} \tag{R2}
\end{align}
If you apply: (1) ...
- 2,246
6
votes
How to determine the charge of amino acid at certain pH?
Behaviour of amino acids in water solution
Amino acids exist in the solution in the form of zwitterions (molecules that contain an equal number of positively and negatively charged functional groups). ...
- 546
6
votes
Accepted
Equilibrium constant magnitude for concentration vs. pressure
This is a classical scaling issue. For example, is a $1$ ton object lighter than a $100$ milligram object?
The rule that $K>1$ or $K<1$ should not be taught because it will lead to exactly the ...
- 39.1k
6
votes
Effect of inert gas on the rate of reaction
In the gas phase in so called 'Unimolecular Reactions' an inert gas does play a vital part by collisionally exciting a potentially reactive molecule. The scheme is
$$\ce{A + M } \overset{k_2}{ \...
- 30.1k
6
votes
Understanding Reaction Rates and equilibria
At $t=0$ the forward rate $A\to B$ is at a maximum, as $\ce{[B] = 0}$ (assuming only A at the start) and after a second or so some B is present and rate $A\to B$ has reduced a bit as there is less $A$ ...
- 30.1k
5
votes
Accepted
Calculate the titer of a solution
Your approach is correct, although there is no information about which solution is considered as ideal, and which is real. It is also a pity you are not able to be more precise than $0.022$ liter as a ...
- 27.1k
5
votes
Does it make any sense to graph 1/T versus ln(Kc)?
As
\begin{align}
Δ_\text{r}G°&=-RT\ln{(K)}\\
Δ_\text{r}G°&= Δ_\text{r}H° - TΔ_\text{r}S°
\end{align}
then
\begin{align}
\ln{(K)} = -\frac{Δ_\text{r}G°}{R}\cdot \frac{1}{T} &= - \frac{Δ_\...
- 39.5k
4
votes
Calculate the titer of a solution
Wikipedia is not the ultimate resource for classical volumetric titrations. This is why textbooks still exist. The definition of titer given in Wikipedia has nothing to do with the classical meaning ...
- 39.1k
4
votes
Successive deprotonation - how far can it go?
It depends on the pH value of the solution / the (remaining) presence of a base sufficiently strong if you have a significant concentration of $\ce{H2SO3}$ (note the note), $\ce{HSO^-_3}$, and $\ce{SO^...
- 28.4k
4
votes
Why do we say the position of equilibrium is shifted even when K is the same?
Maybe you understand better with a simple numerical example.
Suppose we are dealing with an equilibrium reaction A + B <=> C + D, where the equilibrium constant $K$ is $K = \frac{[C][D]}{[A][B]}$...
- 27.1k
3
votes
Can ICE tables give two answers?
$$4.00\cdot 10^{-2}=\frac{(0.080-2x)^{2}}{(0.100+x)(0.100+x)}=\frac{(0.080-2x)^2}{(0.100+x)^2}=\left(\frac{0.080-2x}{0.100+x}\right)^2=0.040$$
Taking the square root on both sides:
$$\frac{0.080-2x}{0....
- 1,345
3
votes
Why is the voltage produced by a voltaic cell affected by temperature as described by the Nernst Equation?
Both terms of the difference in the Nernst equation depend on the temperature.
$$E = E^\circ - \frac{R T}{z F} \ln Q$$
The second term obviously depends on temperature because it contains the ...
- 39.2k
3
votes
Accepted
Change of equilibrium constant with respect to temperature
There is no need to invoke the Arrhenius equation to understand it. I will give the various form of that equation so you are out of doubts.
The significance is clear when you go back to the ...
- 2,246
3
votes
Higher or lower temperature to produce maximum yield of NH3(g) in Haber process
The book is right, and so is your teacher.
The reaction is exothermic, $\ce {N2 + 3 H2 -> 2 NH3}$, ΔH° = -91.8 ~kJ/mol, so higher temperature leads to decomposition, i.e., makes $\ce{2 NH3 -> ...
- 30.5k
2
votes
Why does Le Chatelier's Principle hold when the volume of a system is decreases?
In the Arrhenius Equation, the value, Z, doesn't change with a change in volume. This is because, in collision theory, it represents the frequency of collisions at a specific or standard concentration ...
- 2,037
2
votes
Which one is nitric Acid, HNO3 by itself, or when it is included in H2O?
Different compounds and mixtures are described as nitric acid
Depending on context and use several chemicals are described as "nitric acid".
The common laboratory chemical usually called ...
- 35.5k
2
votes
Why is the theoretical value of the electrode potential different to the experimental value for Cu and Al for a galvanic cell by using Nernst equation
Don't use an aluminium electrode. In the presence of air, aluminium is always covered by a thin, continuous, colorless, insulating and waterproof layer of alumina (Aluminium oxide $\ce{Al2O3}$). If ...
- 27.1k
2
votes
Why can't the product of an acid reacting with water react with water itself and produce OH-?
I really like this question because it digs at wanting to understand what's going on beneath the equations you've been given to know why that equation works.
Orthocresl answered it really well, but I ...
- 21
2
votes
Calculate the pH at the equilibrium point in an acetic acid sodium hydroxide titration
At the equivalence point, there is excess neither of acetic acid neither of sodium hydroxide. The solution is equivalent to the solution of sodium acetate of the concentration $\pu{0.1 M}$, as both ...
- 39.5k
2
votes
Accepted
How does an equilibrium move when increasing the concentration of water?
I have the following equilibrium given:
$$\ce{[Co(H2O)6]^2+(aq) + 4 Cl-(aq) <=> [CoCl4]^2-(aq) + 6 H2O(l)}$$
This above equation may rather confuse you, for your purpose is better to write it ...
- 39.5k
2
votes
Accepted
Which way Le Chatelier's principle
This can get confusing. What you seem to have expressed is you want to reduce the effect of an increased external force by increasing the internal pressure. This can be done in such a situation of a ...
- 1,820
2
votes
Can ΔG = ΔG° + RT ln Q be used to calculate K at different temperatures?
As mentioned in the comments, $K$ is itself temperature dependent. That is to say, $K = K(T)$ is a function of temperature, so
$$\Delta_\mathrm{r} G^\circ = -RT\ln K(T)$$
and the temperature ...
- 71.1k
Only top scored, non community-wiki answers of a minimum length are eligible