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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Why is a theoretical titration curve higher than a practical one?

I'm currently in high school and I did two titrations. The first one is a titration of $10.0~\mathrm{mL}$ $0.1~\mathrm{M}$ $\ce{HCl}$ with $x~\mathrm{mL}$ $\ce{NaOH}$. I obtained the following ...
Tim Vermeulen's user avatar
15 votes
4 answers
71k 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 ...
Eliza's user avatar
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13 votes
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Why are synthetic pH indicators used over natural indicators?

Synthetic indicators seem to be exclusively used when determining the pH of a substance with an indicator (with the exception of that school experiment where you boil cabbage to demonstrate natural pH ...
Patrick Shway's user avatar
12 votes
1 answer
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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 ...
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12 votes
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How do I calculate the concentration of sulphuric acid by a titration experiment with sodium hydroxide?

In my latest chem lab the objective was to create a primary standard of $\ce{NaOH}$ and use it to determine the concentration of sulfuric acid. The first part of the lab was determine the molarity of ...
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11 votes
1 answer
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Why is Borax used as a primary standard?

It's given in my book that borax is a useful primary standard for titrating against acids. I have heard that primary standard is a pure reagent and does not gain any weight by absorbing moisture. (...
Aditya Dev's user avatar
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10 votes
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What are the limitations of the Hendersson-Hasselbalch equation?

Our instructor told us that prior to the equivalence point, the $\mathrm{pH}$ of a solution is dependent on the HH equation. However, when I tried practicing for polyprotic acid titration, I came upon ...
Kent de los Reyes's user avatar
10 votes
1 answer
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How is the the law of chemical equivalence defined and what are its limitations?

I've heard that the law of chemical equivalence states that the gram equivalence of each of the reactants equals the gram equivalence of each of the products. But I'm facing difficulties in ...
Mathejunior's user avatar
10 votes
1 answer
623 views

How to derive the conductivity titration curve which accounts for salt formation

I derived an equation that gave me the volume of base required to get a certain $\mathrm{pH}$: In a titration between a weak acid $\ce{HA}$ and weak base $\ce{B}$ (adding base into acid solution) the ...
sab hoque's user avatar
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3 answers
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How do we calculate N factor and why is it useful in calulations?

I don't understand the concept of N factor at all. Why is it important? I know that it is something dependent upon the oxidation number, for example N factor of Na would be 1 since it has oxidation ...
user3397's user avatar
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9 votes
1 answer
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Why isn't sodium hydrogen phthalate used instead of KHP?

Why is potassium hydrogen phthalate (KHP) ubiquitously synthesized and used as a primary standard, while sodium hydrogen phthalate isn't even available to buy?
1__'s user avatar
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9 votes
2 answers
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How to (numerically) model a phosphoric acid titration curve

I've been learning how to simulate a 1M phosphoric acid titration curve using numerical methods in R. So far has this has been the best curve: Notice how it flattens out (artificially) towards the ...
Naiky's user avatar
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2 answers
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Use of pipette during experiments for determination of oxygen by Winkler's method

We were performing estimation of $\ce{O2}$ by Winkler's method and we were told by the instructor that while adding $\ce{MnSO4}$ and $\ce{NaOH}$ / $\ce{KI}$ the pipette tip should be well below the ...
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3 answers
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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}]}{[\...
Tony's user avatar
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3 answers
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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 ...
Sushanth Saha's user avatar
8 votes
2 answers
16k views

Why, in titration, is universal indicator not commonly used?

My teacher said that we always used indicators such as methyl red, methyl orange, litmus, phenolphthalein, etc. rather than universal indicator. I don't understand why, though, would not universal ...
Cameron Eggins's user avatar
8 votes
2 answers
27k views

Why are strong acids and bases not suitable as primary standards?

This is one of the questions with which I have puzzled over, and can arrive at no definite conclusion. Why are strong acids or bases, such as $\ce{H2SO4}$,$\ce{ HNO3}$, $\ce{HCl}$, and $\ce{NaOH}$ not ...
Bidella's user avatar
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8 votes
2 answers
477 views

What is the meaning of cmmol in chemistry?

I came across a unit called $\text{cmmol dm}^{-3}$ in buffer solutions. What does this unit mean?
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8 votes
2 answers
14k views

Find the initial volume of the weak acid given a titration graph

Question: Below is a picture of a titration between a weak acid, $\ce{HA}$, and a 0.150 M $\ce{NaOH}$ solution. Find the initial volume of the weak acid in milliliters in this titration. My ...
krismath's user avatar
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8 votes
3 answers
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Volume required to dilute solution for a pH change

A $\pu{100 mL}$ solution of $\ce{NaOH}$ has a $\mathrm{pH}$ of $13$. What volume of water in $\pu{mL}$ must be added to change the $\mathrm{pH}$ to $11$? My steps: Begin by calculating conc. of $[\...
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Brown color at end point during titration with phenolphthalein as indicator

We did a titration experiment at school and I did not understand one part of it. The scenario: Titrate : White wine (ethanoic acid) Titrant: $\ce{NaOH}$ Indicator: Phenolphthalein What happened:...
Bad at chemistry's user avatar
8 votes
1 answer
785 views

Why do these two calculations give me different answers for the same acid-base titration?

In class, I performed an weak acid-strong base titration using commercial white vinegar and sodium hydroxide with the aim of finding the concentration of of ethanoic acid in the vinegar, and I used ...
Razorlance's user avatar
8 votes
0 answers
15k views

How to determine the iron content in spinach from a titration with permanganate solution?

I used titration to find the mass of iron in a $5~\mathrm{g}$ sample of spinach after leaving the spinach to soak in tap water for five different lengths of times. I added $\ce{H2SO4}$ to the solution ...
SophieH's user avatar
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7 votes
6 answers
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Best regression model for a sigmoidal pattern

Students submit the data for an acid–base titration to my app. The abscissa axis corresponds to the volume. Along the ordinate axis are the pH values. The curve I’m looking for must work automatically ...
krirkrirk's user avatar
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7 votes
2 answers
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Amount of Phenolphthalein required

We just had chemistry practical few days a go. The topic was strong acid-base titration, in which we had to find the normality and concentration of $\ce{HCl}$. My teacher instructed me to add 2 drops ...
Freddy's user avatar
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7 votes
1 answer
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Why does phosphoric acid mask the colour of iron(III) complex in water?

In the redox titration of iron(III) with permanganate or dichromate, we use phosphoric(V) acid to "mask" the color of iron(III) because it interferes with the end point color change. What's the ...
user24665's user avatar
  • 115
7 votes
2 answers
17k views

What is causing the buffer region in a weak acid - strong base titration?

For the buffer region in this, why does it stop the pH from increasing? At the start: $$\ce{CH3COOH + NaOH -> CH3COONa + H2O}$$ Which means there will be a high amount of salt in the solution, ...
user45953's user avatar
7 votes
1 answer
191 views

How did early chemists measure concentrations and purity?

My chemistry teacher loves going back through the history of famous chemists. This got me wondering how these chemists would first determine the concentration of a sample before they had any other ...
Guest's user avatar
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7 votes
1 answer
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How can one optimise the formation of copper acetate?

Mixing solid copper, $5\%$ vinegar, and hydrogen peroxide ($\ce{H2O2}$) causes copper acetate to form. The process will occur very slowly without hydrogen peroxide. Adding $\ce{H2O2}$ speeds the ...
Dale's user avatar
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7 votes
1 answer
17k views

Sodium carbonate titration in presence of phenolphthalein

Why phenolphthalein cannot show the endpoint for the complete titration of Na2CO3 with only phenolphthalein? What's the reason that we consider only half of the moles of sodium carbonate when ...
bulbasaur 's user avatar
7 votes
2 answers
8k views

Weighing by difference

When preparing a known mass of something (e.g. when producing a standard solution) it is often that in my school lab that we first use a weighing boat to measure the mass and then once transferred ...
Jake's user avatar
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7 votes
3 answers
25k views

Why the colour of KMnO4 at the end point of titration may disappear after some time?

In the redox titration of $\ce{FeSO4}$ with $\ce{KMnO4}$, the colour change of the solution at the end point is colourless to light pink. Most laboratory manuals and books advice us to check whether ...
S R Maiti's user avatar
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7 votes
2 answers
281 views

Is there a potentiometric method for monitoring salt formation in organic solvent?

I work in a pharmaceutical R+D lab, and currently aim to develop a validatable potentiometric method for determining the optimal amount of acid to add to a basified small organic molecule for ...
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6 votes
1 answer
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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?
Bertha Aguilar's user avatar
6 votes
1 answer
87k views

Why is phenolphthalein an appropriate indicator for titration of a strong acid with a strong base?

How does the pH at the equivalence point, as well as the pH range over which the colour of phenolphthalein changes, make it a suitable indicator for titrations between strong acids and strong bases?
skateboard34's user avatar
6 votes
2 answers
3k views

Why does the pH before the equivalence point of a titration depend on the initial concentration only when the acid is strong?

SO, in this picture, two different titration curves are shown: one for a weak acid, one for a strong acid. I'm confused as to why for a strong acid, if you vary the concentration of the acid, (and the ...
Brayden Murphy's user avatar
6 votes
1 answer
119 views

How much additional hydrochloric acid should be added to arrive at ‘excess acid’?

I am an IB student. And I am trying to find the mass percentage of $\ce{NaHCO3}$ in antacid. I am dissolving the antacid in $\pu{0.1 M}$ $\ce{HCl}$ solution. So, first of all I conducted some ...
Selena Carlos's user avatar
6 votes
2 answers
1k 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 ...
John Snow's user avatar
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6 votes
1 answer
165 views

How do you experimentally calculate the ionization constant of the carbonate ion?

Given sodium hydrogen carbonate, $\ce{NaHCO3}$, as well as hydrochloric acid, $\ce{HCl}$, how would you experimentally determine the ionization constant for the carbonate ion, $\ce{HCO3-}$? By ...
Kyle Anderson's user avatar
6 votes
1 answer
16k views

Deriving the equation for oxygen estimation by Winkler’s method

We were doing $\ce{O2}$ estimation by Winkler's method The procedure and reactions involved in this experiment are: Carefully fill a 300-mL glass stoppered bottle brim-full with sample water. ...
Tyto alba's user avatar
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6 votes
1 answer
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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 ...
icesk8er's user avatar
6 votes
1 answer
1k views

What would one have to do differently if they used NaMnO4 instead of KMnO4 for redox titrations?

I am doing a chemistry report related to redox titrations (using $\ce{KMnO4}$ as the titrant), and one section of the report asks me to explain what would occur if I were to use sodium permanganate ($\...
Admin Voter's user avatar
6 votes
1 answer
222 views

Is this problem about acid-base titration wrong?

I wouldn't post mere 'problems' here normally, but I will hopefully be starting to give chemistry education to some 10-11-12th graders and I want to make sure that it is not I that has a problem but ...
Emirhan G.'s user avatar
6 votes
1 answer
2k views

Which method can be used to determine the pKa of an acid-base indicator like bromothymol blue?

I have a question about how one would determine the pKa of an acid-base indicator such as bromothymol blue. I know that spectrophotometric analysis is one option, but is it possible to perform an ...
strugglebus's user avatar
6 votes
1 answer
1k views

Error in Titration

When doing a titration with a burette, the error of the burette is usually $\pm 0.05\ \mathrm {ml}$, as we have to read two times on the burette (initial/final vol), the error will be $\pm 0.07\ \...
user164612's user avatar
5 votes
5 answers
126k views

What role does sulfuric acid play in the titration of oxalic acid and potassium permanganate?

The titration is between oxalic acid and potassium permanganate, with $\ce{H2SO4}$ added to oxalic acid. My question is what role other than a dehydrating agent and maybe catalysing does the $\ce{...
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5 votes
2 answers
305 views

Should the tip of the burette of an automatic titrator be immersed in the analyte?

In all the tutorials I found online, the tip of the burette (containing the titrant - NaOH) was immersed into the analyte solution. My question is: shouldn't the tip be out of the solution? Isn't ...
Zaid assaf's user avatar
5 votes
1 answer
1k views

NaOH Normality Slowly Changing

Our lab uses a sodium hydroxide solution of a (theoretically) known normality (0.8000 - 1.0000) to titrate product samples for quality control. However, we suspect that the normality of the $\ce{NaOH}...
realityChemist's user avatar
5 votes
1 answer
1k views

How to get a precise reading from pipette?

While doing titrations, we are instructed to use pipette and they demonstrated how to use a pipette. But still after all this, we face difficulties of how to take precise reading from pipette. ...
Shashank's user avatar
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5 votes
2 answers
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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{...
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