NTA Abhyas JEE Main2020Chemistryp Block Elements (Group 13 & 14)Practice
Which is not true about borax?
Options
- AIt is a useful primary standard for titrating against acids
- BOne mole of borax contains 4 B - O - B bonds
- CAqueous solution of borax can be used as buffer
- DIt is made up of two triangular B O 3 units and two tetrahedral B O 4 units
Correct answer
B. One mole of borax contains 4 B - O - B bonds
Step-by-step solution
Here only in option B is incorrect while rest other are correct. In borax N a 2 B 4 O 7 . 10 H 2 O , among 10 water molecules 2 molecules are part of structure, i.e., exists N a 2 [ B 4 O 5 ( O H ) 4 ] . 8 H 2 O N a 2 [ B 4 O 5 ( O H ) 4 ] . 8 H 2 O + 2 H C l → 2 N a C l + 4 H 3 B O 3 + 5 H 2 O Methyl orange (pH = 3.7) is used to detect end point. Aqueous solution of borax acts as buffer, as borax is salt of strong base NaOH and weak acid H 3 B O 3 .