Answer : The original concentration of copper (II) sulfate in the sample is, 
Explanation :
Molar mass of Cu = 63.5 g/mol
First we have to calculate the number of moles of Cu.
Number of moles of Cu = 
Now we have to calculate the number of moles of 
Number of moles of Cu = Number of moles of 
Number of moles of
= 
Now we have to calculate the molarity of 

Now put all the given values in this formula, we get:

To change mol/L into g/L, we need to multiply it with molar mass of 
Molar mass of
= 159.609 g/mL
Concentration in g/L = 
Thus, the original concentration of copper (II) sulfate in the sample is, 
Answer:
D
Explanation:
Silver is a metal with high conductivity ....
Hope its right !
Answer:
B
Explanation:
It is important to only test one variable at a time because you need to be able to disprove or prove a problem with just one independent variable. When you have several variables in the experiment, it would be impossible to know which variable honestly caused the end result.