Introduction to Indicators

 Hello fam! Welcome back from the short break. I believe that we are all enjoying the summer holidays. We will now continue from a new topic after we discussed about salts last week.


Today, we want to look at the concept of indicators. We need to know that an indicator is a substance that changes color in the presence of an acid or a base. 


The idea of the color change is the first thing that you have to bear in mind about the indicators. Many of us have at one time or another titrated an acid against a base or vice versa. 


The point at which the acid and base have completely reacted in accordance with the stoichiometry of the reaction equation is called the equivalence point.


Let me give you a typical example; Look at the reaction;

2NaOH(aq) + H2SO4(aq) -- Na2SO4(aq) + 2H2O(l)

This reaction would be complete when two moles of sodium hydroxide react with exactly one mole of sulfuric acid. In other words, the amount of titrant added is just enough to neutralize the analyte solution.


How do I know when the amount of titrant added is just enough to neutralize the analyte solution? I have to depend on some kind of reagent  that would visually indicate this point.


Any reagent that can visually indicate the point at which the amount of titrant added is just enough to neutralize the analyte solution is called an indicator.


The indicator solution has a different color in acidic, basic and neutral solutions. Hence, an indicator solution is added in drops to an acid or base analyte solution before the titrant is added. The point at which the color of the solution changes during titration is the equivalence point of the solution.


In everyday experiments in the laboratory, we use the endpoint to determine the amount of substance present in an analyte during volumetric analysis. The end point and the equivalence point are not exactly the same. However, we approximate the both to be equal for convenience sake.


The equivalence point is accurately determined from a titration curve and we shall look at that in due course. How exactly does an indicator work? Join us tomorrow to know more!


Hope you enjoyed our lesson today?

Follow  our page  and share!

Do you have assignments, term papers, projects and difficult homework questions? Contact us for help now! We also offer home and remote tutoring services to students at all levels in science subjects.








Comments

Post a Comment

Popular posts from this blog

Definition of acids 2 - Introduction to Lewis Acids

Image
 Hello fam! Welcome to today’s lesson. We started to look at the concept of acid definition in yesterday’s lesson. We saw yesterday that acids have been defined by Arrhenius and BrØnsted – Lowry. The Arrhenius definition is limited in the sense that it does not account for behavior of acids in nonaqueous media. Did you try the assignment yesterday? The answers are attached to this post. I believe that the concept of proton donation is now clear to you after looking at the images attached. Reach out to me if you have any challenge. Now let us talk about the Lewis definition of acids. This definition of acids was put out by G. N Lewis in 1923. There is a foundation that we need in order to have an understanding of the idea that was put forward by Lewis.  There is something called an orbital in an atom. It is a region in space where there is a high probability of finding the electron. Now let us assume that your office is at No.38 Bronx street. I may not find you everywhere in the compoun
Read more

Calculations on pKa and pH

Image
 Hello! I heartily welcome you all to today’s lesson. We are going to look at the last two calculations that pertain to pH, acids and bases today and tomorrow we would commence our discussion on salts to pave way for a discussion on buffers. I hope all the topics so far are making sense? Your feedback would be highly appreciated. Example 8; What is the pH of 0.2 M solution of sodium acetate. The pKa of acetic acid is 1.8 * 10^-5. Solution; We have that the hydrolysis of sodium acetate occurs as follows; CH3CH2COONa(aq) <-> CH3CH2COO^-(aq) + Na^+(aq)    CH3CH2COO^-(aq) + H2O(l) <-> CH3CH2COOH + OH^-(aq) We can see that that the acetate ion acted as a base hence it accepted a proton. We would have to obtain the Kb Kb = 1 * 10^-14/Ka Kb = 1 * 10^-14/1.8 * 10^-5 Kb = 5.6 * 10^-10 Setting up the ICE TABLE, we have that;          CH3CH2COO^-(aq) + H2O(l) <-> CH3CH2COOH + OH^-(aq) I            0.2                                                      0                       
Read more

Bonding in Complex Salts

Image
 Hello! yesterday, we started looking at the complex salt which we called tetramine copper II chloride with the formula; [Cu(NH3)4]Cl2. We did say that this is a complex salt because of the presence to the complex cation [Cu(NH3)4]^2+. I want to state that if we had a complex anion, the salt would also be a complex salt. A typical example of this is; K4 [Fe(CN)6]. The complex ion is  [Fe(CN)6]4- which is anionic and the counter ions in this case are potassium cations. I told you that we will look at the bonding in the complex salt [Cu(NH3)4]Cl2 and why it does not produce simple ions in water. I will try to explain the basics of the concept today as we would still look at coordination chemistry in more detail sometime later.  Now, the complex salt [Cu(NH3)4]Cl2 has both ionic and covalent bonds. The four ammonia molecules are attached to the central copper II ion by a coordinate covalent bond(see the page timeline for an explanation of what a coordinate covalent bond is). We showed the
Read more