Class 11th

This is a Multiple Choice Questions as classified in NCERT Exemplar

B

The four terminal hydrogen atoms and two boron atoms are all in the same plane.

There are two bridging hydrogen atoms above and below this plane.

The four terminal B-H bonds are regular two-centre-two-electron bonds, whereas the two bridge (B-H-B) bonds are unique and can be described as three-centre-two-electron bonds, as shown in figure:

This is a Multiple Choice Questions as classified in NCERT Exemplar

C

Me₃SiCl is a soleuless liquid That has a major application in the formation of silicones. On its addition in the process, it blocks the end and controls the chain length of the polymer.

This is a Multiple Choice Questions as classified in NCERT Exemplar

B

In group 14, as we move down from C to Sn, the size increases and electronegativity decreases. This results in the decrease in M-M bond energy. Hence the catenation property decreases.

Bond energy is the amount of energy required to fragment the atoms combined in a molecule are born into separate atoms. Carbon has maximum bond energy as compared to its other group elements. Therefore, shows maximum catenation property.

This is a Multiple Choice Questions as classified in NCERT Exemplar

C

Boric acid is Lewis acid, having six electrons in its valence shell. It combines with water, accepts electrons

from OH⁻of water molecule and complete it octet to 8 and releases H⁺

Reaction: B (OH)₃ + OH − H→ [B (OH)₄]⁻ + H⁺

This is a short answer type question as classified in NCERT Exemplar

Let b be the position vector of the centre of mass of a regular n-polygon.

(n-1) equal point masses are placed at (n-1) vertices of the regular n polygon, therefore for its centre of mass

r_CM= $\frac{\left(n-1\right)mb+ma}{\left(n-1\right)m+m}=0$

(n-1)mb+ma=0

B=- $\frac{a}{n-1}$

This is a Multiple Choice Questions as classified in NCERT Exemplar

A

Number of items/molecules bonded to the central atom is termed as coordination number. In the given MF₆³⁻

Coordination number of metal is six and boron can have topmost coordination number of four as it consists of s and p orbital only and lacks d-orbital. Therefore, boron cannot be compared in the form of MF₆³⁻.

This is a Multiple Choice Questions as classified in NCERT Exemplar

A

The B₂O₃ reacts with water to form boric acid hence it is an acidic oxide. As we move down the group electronegativity decreases and the tendency to donate electrons increases therefore basic character increases or acidic character decreases. So, from the given options, the most acidic oxide is B₂O₃.

This is a short answer type question as classified in NCERT Exemplar

Where weight of the door acts along negative y axis

A force can produce torque only along a direction normal to itself as $\tau =r*F$ . So when the door is in the xy plane the torque produced by gravity can only along z direction. Never about an axis passing through y direction. Hence the weight will not produce any torque.