What are the limitations of litmus paper and Phenolphthalein indicators? Name to other indicators that can be used that do not h
ave such limitations
1 answer:
Answer:
Here's what I find.
Explanation:
An indicator is usually is a weak acid in which the acid and base forms have different colours. Most indicators change colour over a narrow pH range.
(a) Litmus
Litmus is red in acid (< pH 5) and blue in base (> pH 8).
This is a rather wide pH range, so litmus is not much good in titrations.
However, the range is which it changes colour includes pH 7 (neutral), so it is good for distinguishing between acids and bases.
(b) Phenolphthalein
Phenolphthalein is colourless in acid (< pH 8.3) and red in base (> pH 10).
This is a narrow pH range, so phenolphthalein is good for titrating acids with strong bases..
However, it can't distinguish between acids and weakly basic solutions.
It would be colourless in a strongly acid solution with pH =1 and in a basic solution with pH = 8.
(c) Other indicators
Other acid-base indicators have the general limitations as phenolphthalein. Most of them have a small pH range, so they are useful in acid-base titrations.
The only one that could serve as a general acid-base indicator is bromothymol blue, which has a pH range of 6.0 to 7.6.
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Answer:
"0.60 g" is the appropriate solution.
Explanation:
The given values are:
Volume of base,
= 30 ml
Molarity of base,
= 0.05 m
Molar mass of acid,
= 400 g/mol
As we know,
⇒
On substituting the values, we get
⇒
⇒
⇒
hence,
⇒
On substituting the values, we get
⇒
⇒
⇒
This problem is asking for an explanation of what we need to know about double and triple bonds to successfully predict molecular geometries in molecules. At the end, one comes to the conclusion that double and triple bonds contribute to the degree in which an atom is bonded and they also determine the lone pairs, which, at the same time, define the molecular geometry.
<h3>Molecular geometry:</h3>In chemistry, molecules are not necessarily flat arrangements of atoms, yet they have specific bond angles, orientations and shapes, which define the molecular geometry. In such a way, we can use the VSEPR theory in order to know the molecular geometry of a molecule; however, we first need its Lewis structure or at least the number and type of bonds to do so.
Consider water and carbon dioxide; the former has two hydrogen to oxygen bonds (O-H) and 2 lone pairs because O has six valence electrons but just 2 are bonded to complete the octet, so 4 unpaired electrons lead to two lone pairs. On the other hand, the latter has two double bonds (C=O) and 0 lone pairs because carbon has four valence electrons and they are all bonded to complete the octet.
In such a way, one can see how the double bond affected the bonding in CO2 in contrast to the H2O; situation that also applies to triple bonds, because CO2 has a linear molecular geometry whereas water has a bent one (see attached picture)
Hence, one comes to the conclusion that double and triple bonds contribute to the degree in which an atom is bonded and they also determine the lone pairs, which, at the same time, define the molecular geometry.
Learn more about molecular geometry: brainly.com/question/7558603
Learn more about the VSEPR theory: brainly.com/question/14225705
