Question

Given below are two statements : 
Statement I : Upon heating a borax bead dipped in cupric sulphate in a luminous flame, the colour of the bead becomes green.
Statement II : The green colour observerd is due to the formation of copper(I) metaborate.
In the light of the above statements, choose the most appropriate answer from the options given below :

• A. Both Statement I and Statement II are false
• B. Both Statement I and Statement II are rue
• C. Statement I is false but Statement II is true
• D. Statement I is true but Statement II is false

Hint:

In the Borax Bead Test, the formation of cupric metaborate gives the bead its blue-green colour in the reducing flame, not copper(I) metaborate.

Answer 1

The Correct Option is A

To solve the given question, we need to analyze both statements I and II individually and then in relation to each other.

Analysis of Statement I:

Statement I: Upon heating a borax bead dipped in cupric sulphate in a luminous flame, the colour of the bead becomes green.

The borax bead test is a classic technique in qualitative inorganic analysis to detect the presence of certain metal ions. When a borax bead is exposed to different flame types and metal ions, it can display distinct colors.

When a borax bead containing copper ions (from cupric sulphate) is heated in a flame, it typically displays a blue or green hue. However, the luminous flame, which is generally less oxidizing, causes the bead to turn blue or remain light blue due to copper(II) compounds. Hence, statement I, implying the bead always turns green in a luminous flame due to this specific reaction, is incorrect.

Analysis of Statement II:

Statement II: The green colour observed is due to the formation of copper(I) metaborate.

The color changes that occur during the borax bead test with copper compounds are not generally attributed to copper(I) metaborate. Instead, the green or blue colors are often due to copper(II) compounds, such as copper(II) oxide or copper(II) metaborate, especially in an oxidizing flame like a Bunsen burner flame. The formation of copper(I) metaborate is unlikely, thus making statement II false.

Conclusion:

Both Statement I and Statement II are indeed false, which justifies the correct answer:

• Both Statement I and Statement II are false