Answer:
Mass of 1 mole of copper is 63.83 g.
0.03916 moles of copper atoms have a mass equal to the 2.5 grams of copper penny.
Explanation:
Mass of 1 copper atom,m = 

Mass of 1 mole of copper :
= 
Mass of 1 mole of copper = 63.83 g
Mass of copper penny = 2.5 g
Atomic mass of copper = 63.83 g/mol
Moles of copper in 2.5 g of copper penny:

0.03916 moles of copper atoms have a mass equal to the 2.5 grams of copper penny.
One kilogram is equal to one thousand grams. Further, one gram is equal to 1000 mg. The conversion is as shown below,
(6.285 x 10³ mg) x (1 g / 1000 mg) x (1 kg / 1000 g)
The numerical value of the operation above is 0.006285 kg.
Answer:
Explanation:
Efficiency of the electric power plant is 
Here Temperature of hot source 
and Temperature of sink 
Hence the efficiency is
Now another formula for thermal efficiency Is

Here QI is the of heat taken from source 100 MJ ; Q2 of heat transferred to the sink (river) to be found
W is the of work done and W = QI -Q2
Hence From

Hence the of heat transferred to the river Is 
Answer/Explanation:
Wave W is being diffracted, Wave X is being reflected, and waves Y and Z are being refracted.