Taking into account the definition of molar mass,
In first place, the rule of three is a way of solving problems of proportionality between three known values and an unknown value, establishing a relationship of proportionality between all of them.
That is, what is intended with it is to find the fourth term of a proportion knowing the other three.
If the relationship between the magnitudes is direct, that is, when one magnitude increases, so does the other (or when one magnitude decreases, so does the other) , the direct rule of three must be applied.
To solve a direct rule of three, the following formula must be followed, being a, b and c known data and x the variable to be calculated:
a ⇒ b
c ⇒ x
So: [tex]x=\frac{cxb}{a}[/tex]
The direct rule of three is applied in this case, knowing that the molar mass of Cu is 63.54 [tex]\frac{g}{mole}[/tex], this is the amount of mass a substance contains in one mole.
So: if 63.54 grams of Cu are contained in 1 mole, 65.8 grams of Cu are contained in how many moles?
63.54 grams ⇒ 1 mole
65.8 grams ⇒ x
So: [tex]x=\frac{65.8 gramsx1 mole}{63.54 grams}[/tex]
[tex]x= 1.04 moles[/tex]
Finally, the correct answer is option A. 1.04 moles of copper (Cu) are in 65.8 g Cu.
Learn more with this example:
