Class 11th

It's not always true. Direction of velocity is the most important consideration here that will tell us whether acceleration increases or decreases speed. You can consider two scenarios. If you're falling, that's negative velocity. That implies negative gravitational acceleration. Here, your speed increases. If you're moving upward, that's positive velocity. Now, with that same negative acceleration, your speed decreases. For choosing the equations of motion, you need to know both the signs of acceleration and velocity to determine if you're speeding up or slowing down.

Zero velocity doesn't mean zero acceleration. When you throw a ball-like object upward, at its peak the velocity is zero. But acceleration remains constant due to gravity. The velocity is still changing from positive to negative at that instant. That means acceleration continues.

Reduced pressure distillation technique is used for purification of high boiling organic liquid which decompose near its boiling point. By reducing pressure they boil below their normal boiling point.

Solubility of gas in liquid increases on decreasing the temperature. So water at 4°C will have more dissolved O₂.

Aniline being a base does not give Friedel Craft reaction because it react with AlCl₃ used in Friedel Craft reaction.

Ba has outer electronic configuration 6s².

CaC₂O₄ is insoluble in water.

Compound of Li are covalent so soluble in organic solvent.

Na forms strong monoacidic base.

So; A is H₃PO₂ & B is CH₃ – CH₂ – Cl

3-Ethylhex-3-ene will not show stereo isomerism

Methylhex-1-ene will show steroisomerism (optical isomerism)

Since it has chiral carbon.

3, 4-Dimethylhex-3-ene will show stereoisomerism (Geometrical isomerism)

4-Methylhex-1-ene will show stereoisomerism (optical) since it has one chiral carbon

$2NaB{H}_4+l_2\to 2Nal+H_2+B_2{H}_6$

Diborane is produced when NaBH₄ is reacted with I₂

Both boron atoms are sp³ hybridised & molecule is non-planar. Diborane as two bridged 3 centre-2-electron bonds.