Questions tagged [titration]

A laboratory method to determine the concentration of an analyte in solution. The solution volume plays a key role in the analysis.

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11
votes
4answers
52k views

Shouldn't the pH at the equivalence point always be 7?

I learned in class that the equivalence point in an acid-base titration is reached when the solution contains an equal amount of substance of $\ce{OH-}$ and $\ce{H+}$ ions. However, in a weak acid and ...
12
votes
1answer
1k views

How to analyze a acid and salt mixture using titrimetry?

Given a mixture of $\ce{HCl}$ and $\ce{MCl3}$ and the following dissociation constants for $\ce{M(OH)3}$, how can the concentrations of $\ce{HCl}$ and $\ce{MCl3}$ be determined separately by titrating ...
8
votes
3answers
39k views

Calculating Buffer Capacity

I completed a titration of Ammonium Acetate buffer solution and to it I added $\pu{2M}$ Hydrochloric Acid. I measured the initial $\ce{pH}$ of the buffer solution before any acid was added and I ...
5
votes
2answers
3k views

What are the products for the redox reaction HCl + SnCl₂ + KMnO₄?

In the redox reaction, where $\ce{HCl}$ is the excess reactant do these reactions produce following half reactions? \begin{aligned} (1)&&\ce{SnCl2 &-> Sn^{4+} + 2e-}\\ (2)&&\ce{...
4
votes
2answers
551 views

How to calculate the oxidation state and the number of equivalents oxidized with YBa₂Cu₃O₇

I've hit some trouble with these calculations and need help sorting out confusion. In the lab we synthesized $\ce{YBa2Cu3O7}$, per the lab manual $\ce{Y, Ba, O}$ have the usual charges of +3, +2, and ...
3
votes
1answer
6k views

I need to find the Ka of a weak acid in titration with a strong base

I have been working on this lab forever and have not been able to get a $K_\text{a}$ anywhere close to the accepted value. I’m sure I’m missing something really simple. We titrated $\ce{CH3COOH}$ ...
1
vote
1answer
1k views

Law of chemical equivalence

In this reaction, $$\ce{KIO_3 + KI -> I_2}$$ According to law of chemical equivalence, shouldn't $m_{eq}$ of $\ce{KIO_3}$ = $m_{eq}$ of $\ce{KI}$ = $m_{eq}$ of $\ce{I_2}$? However, the book that I ...
1
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2answers
11k views

MaVa = MbVb - Limitations and Uses

We know that for strong acids with a $1:1$ mole ratio between all particles involved are suitable for use with the aforementioned formula for titration problems. I want to know the limits on this ...
-1
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1answer
21k views

Titration curve graph, finding exact point of the equivalence point

I plotted all my data points and made this graph in excel. Now I need to find the volume of titrant required to read the equivalence point, as well as the pH after 18.5 mL of titrant have been added. ...
7
votes
3answers
3k views

Is the Henderson–Hasselbalch equation volume independent?

Looking at this equation $\mathrm{pH} = \mathrm{p}K_\text{a} +\log\frac{[\ce{CB}]}{[\ce{A}]}$ makes me think that it is concentration independent. What I mean is, when we look at $\frac{[\ce{CB}]}{[\...
6
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1answer
4k views

Buffer formation in weak acid/strong base titration?

I'm a little confused about what happens when you titrate a weak acid or base. For example, let's say that you are trying to titrate a weak acid. Based on this question, it seems like the weak acid ...
5
votes
1answer
2k views

Shape of Weak-Strong Acid-Base Titration

I can understand why in any titration, the pH changes really quickly near the equivalent point. However, in a titration of either weak base-strong acid or weak acid-strong base, the weak acid/base ...
5
votes
1answer
2k views

Yellowish tinge during titration of oxalic acid with potassium permanganate

One of the our chemistry practicals involve finding the molarity of an oxalic acid solution by titrating it with standard $\ce{KMnO4}$ solution. The oxalic acid solution is heated and little sulfuric ...
5
votes
1answer
34k views

Calculating pH for titration of weak base with strong acid

Calculate the pH at the equivalence point for the titration of $\pu{0.130 M}$ methylamine ($\ce{CH3NH2}$) with $\pu{0.130 M}$ $\ce{HCl}$. The $K_\mathrm{b}$ of methylamine is ${5.0 \cdot 10^{–4}}$. ...
3
votes
2answers
1k views

How does an acid prevents or discourges oxidation of iron?

In the titration of $\ce{KMnO4}$ with Mohr's salt, I have learned that sulphuric acid prevents oxidation of $\ce{Fe^2+}$ to $\ce{Fe^3+}$ in the solution before the actual titration. How does the acid ...
7
votes
1answer
2k views

Why must NaOH be kept dry during storage?

Why should the Erlenmeyer flask used to store $\ce{NaOH}$ be dry? Why should it be kept covered at all times?
5
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1answer
2k views

The significance of the dissociation constant of an indicator

In the chapter acid-base, I learned about indicators and how they are actually weak acids. This is the equation given in our book: $\ce{HIn + H_2O <=> H_3O^+ + In^-}$ $K_{in}= \left(\frac{[\...
3
votes
1answer
1k views

Minimising the formation of manganese dioxide in the titration of potassium permanganate

For a titration of potassium permanganate into a standard acidified solution of hydrated iron (II) ammonium sulfate, the solution seems to end up brown (due to the formation of manganese dioxide) ...
3
votes
1answer
767 views

How does dilution affect result of titration of jam?

We currently do some pH adjustments of jams (target pH of 3.2) using citric acid, however, when there is a large difference between the starting pH and the target pH this can be quite a time consuming ...
2
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1answer
6k views

Solubility of calcium hydroxide determined by titration

For a lab I had to determine the solubility and $K_{sp}$ of $\ce{Ca(OH)2}$ by performing two different titrations. I am given the formula to find solubility in molarity it is as written below. ...
2
votes
2answers
6k views

How to determine the equivalent weight of CO2

We were estimating dissolved $\ce{CO2}$ in water by American Public Health Association method. It was a titrimetric method using phenolpthalein indicator. Titrant used was $\ce{NaOH}$ and analyte was ...
2
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1answer
16k views

Calculating pH: Weak Acid, Strong Base

This is a question that had me puzzled for quite a while. I feel that information is missing. A weak acid, $\ce{HA}$, $K_a = 1.0$ x $10^{-4}$, is titrated with $\ce{NaOH}$. At the equivalence point,...
2
votes
1answer
3k views

How to quantify caffeine content in coffee?

How do I titrate caffeine from coffee to estimate the percentage of caffeine in coffee? I have tried using iodine solution, sulfuric acid, and sodium thiosulfate to no avail.
2
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1answer
756 views

Potassium permanganate to analyze iron compounds [closed]

In my lab, I used potassium permanganate in order to analyze the amount of iron in a compound with iron in the +2 oxidation state using titration. My question is how would this analysis be different ...
2
votes
1answer
900 views

Why do some salt ions in solution conduct electricity better than others?

My experiment involves a potentiometric titration, and I have used $\ce{AgNO3}$ as a titrant and KCl/KI/deionised water only as an analyte. In the image below of my data, the potential difference as ...
2
votes
2answers
646 views

What does the small, steep curve at the very beginning of a weak acid strong base titration curve come from?

I understand that a buffer solution is being made, but I don't understand why the titration curve is different from a strong acid strong base one (apart from the steeper pH change). I understand the ...
1
vote
1answer
51 views

How a titration curve is affected when a poorly soluble salt is formed?

Suppose that I have $\pu{100 mL}$ solution of strong acid, $\ce{HA}$, at $\pu{0.10 mol L^{-1}}$. This solution is titrated with a strong base solution, $\ce{BOH}$, at $\pu{0.10 mol L^{-1}}$. Suppose ...
1
vote
2answers
208 views

Concentration of a species outside buffer region (polyprotic acid titration)

I'm wondering if you titrate a polyprotic acid, say, $\ce{H3PO4}$, with a strong base, and you successfully pass the first equivalence point and are maybe at the $\mathrm{pH}=\mathrm{pK}_{a2}$ point ...
1
vote
3answers
523 views

How would a pH curve look like for titration of diluted weak base compared to concentrated one?

Let's say I take $\pu{80 g}$ of a weak base, dilute it with $\pu{50 ml}$ of water and titrate it with a strong acid. I get a titration curve. Now I take again $\pu{80 g}$ of the same weak base but ...
0
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1answer
26k views

What is the difference between the titration of a strong acid with a strong base and that of the titration of a weak acid with a strong base?

Which of the following statements best characterizes the difference between the titration of a strong acid with a strong base and that of the titration of a weak acid with a strong base? A) Both ...
-1
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1answer
3k views

Why should colorimetric titration of a weak acid with a weak base not be done in laboratory? [closed]

Why should colorimetric titration of weak acid with a weak base (or vice versa) not be done in laboratory? How can I draw a pH graph for this?
-1
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1answer
458 views

How to calculate the equivalent mass of Na2S2O3? [closed]

Let us consider the following reaction $$\ce{I2 + 2 Na2S2O3 -> 2 NaI + Na2S4O6}$$ Now, in order to calculate the equivalent mass of $\ce{Na2S2O3}$, first I need to calculate it's $n$-factor which ...