Question

Which of the following is not a preliminary test for detecting anions-
(A) Borax bead test
(B) Flame test
(C) Brown ring test
(D)Cobalt nitrate test

Answer 1

Hint : When an atom joins together with a definite ratio then a molecule is formed. Two types of analysis are present in chemistry qualitative and quantitative analysis. In which we can detect the types of ions present in a molecule and how many amount a molecule.

Complete Step By Step Answer:
A molecule is made up of two types of ions in which one is electropositive which loses the electron also known as cat-ion. Most metals are electropositive; they lose electrons. And another is electronegative which gains electrons also known as anion. Mostly nonmetals gain the electrons.
Two types of analysis present in chemistry $\left( 1 \right)$ Qualitative analysis- in which we can detect the type of cat-ions and anions present in a molecule or mixture of salt. This qualitative analysis is done by using different types of tests.
$\left( 2 \right)$ Quantitative analysis- In Quantitative analysis in which we can detect the amount of cat-ions and anions present in a molecule or mixture of salt. This quantitative analysis is done by using different types of tests.
The borax bead test is used in qualitative analysis in which we can detect the type of cat-ion present in a salt in which different colours indicate the different cat-ions present in a salt. Example- Yellow to brown colour indicates the presence of manganese.
Brown ring test, Cobalt nitrate test and flame test are used in qualitative analysis in which we can detect the type of anion present in a salt.
Brown ring test basically used for detection for nitrate ion ( $NO{}_3^ -$ ).
Hence option A is the correct option because it is not used for detection of anion in qualitative analysis.

Note :
Borax bead test is also known as blister test , this method is very useful for detection of what type of metal presents a salt so this is a very important method for qualitative analysis.
Qualitative analysis is very useful technique in research