C2H5 i think by ÷2 on both
Answer:

Explanation:
= Mass of water = 100 g
= Specific heat of water = 
= Mass of copper = 20 g
= Specific heat of copper = 
= Temperature change in water = 
= Temperature change in cooper = 
T = Final temperature of the system
The heat balance of the system is given by

The final temperature of the water is
.
Answer:
using higher concentration of the nucleophile
Explanation:
In SN2 reaction, the attack of the nucleophile on the substrate occurs simultaneously as the leaving group departs. The entering group normally attacks through the back side of the molecule. The reaction is concerted and bimolecular. This implies that the concentration of the nucleophile is important in the rate equation for the reaction. Hence increasing the concentration of the nucleophile will increase the rate of SN2 reaction.