About sixteen feet
The standard diameter of an inch and a quarter copper pipe is 1.25 inches.
Depends how long it is
1.6 gallons of water.
YES there is
5.435 imperial gallons or 6.794 US gallons
I have recently had to join a 1 inch steel water pipe to a new copper 28mm pipe. You can do this using a 28mm comression joint. 1inch is just uneder 28mm in diameter but the compression joint takes up the difference and works without fault or leaks.
This depends on the size of the copper pipe and what class it is. For example, copper pipe half inch class 0 and copper pipe class 3 have a wide weight difference because the wall of the class 3 copper pipe is much thicker.
Yes but why/????
If you had been advised why ask again?
Yes, easily.
10gpm
40