1
JEE Main 2021 (Online) 27th August Morning Shift
MCQ (Single Correct Answer)
+4
-1
In which one of the following molecules strongest back donation of an electron pair from halide to boron is expected?
A
BCl3
B
BF3
C
BBr3
D
BI3
2
JEE Main 2021 (Online) 26th August Evening Shift
MCQ (Single Correct Answer)
+4
-1
Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R).

Assertion (A) : Barium carbonate is insoluble in water and is highly stable.

Reason (R) : The thermal stability of the carbonates increases with increasing cationic size.
A
Both (A) and (R) are true and (R) is the true explanation of (A)
B
(A) is true but (R) is false
C
Both (A) and (R) are true but (R) is not the true explanation of (A)
D
(A) is false but (R) is true.
3
JEE Main 2021 (Online) 26th August Evening Shift
MCQ (Single Correct Answer)
+4
-1
Chalcogen group elements are :
A
Se, Tb and Pu.
B
Se, Te and Po.
C
S, Te and Pm.
D
O, Ti and Po.
4
JEE Main 2021 (Online) 27th July Evening Shift
MCQ (Single Correct Answer)
+4
-1
The correct order of first ionisation enthalpy is :
A
Mg < S < Al < P
B
Mg < Al < S < P
C
Al < Mg < S < P
D
Mg < Al < P < S
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