Answer:- b. +3
Explanations:- Charge of a metal ion is equal to the number of valence electrons it has as it loses these electrons to have its nearest noble gas like electron configuration.
Al has 3 valence electrons and being a metal it loses all of these and so the charge of Al ion is +3. It could be shown as:
So, the right choice is b. 3+.
12.7 grams of copper will be produced.
<h3><u>Explanation</u>:</h3>Copper is placed below zinc in the metal activity series. This means zinc can replace copper from its salt. Here zinc is added to the salt solution of copper sulphate. The reaction involved is
CuSO4 +Zn =ZnSO4 +Cu.
Zinc sulphate is soluble in the solution and rose red copper will be precipitated from the solution.
From the chemical equation we can see that 1 mole of zinc replaces 1 mole of copper. As no mass of zinc added is mentioned we will assume that excess of zinc is added.
Atomic mass of copper = 63.5
Atomic mass of sulphur = 32.
Atomic mass of oxygen = 16.
So molecular mass of copper sulphate = = 159.5.
So, mass of 1 mole of copper sulphate is 159.5 grams.
So, in 31.9 grams of copper sulphate, number of moles of copper sulphate present = = 0.2
In 1 mole of copper sulphate, 1 mole of copper is present.
So in 0.2 moles of copper sulphate, 0.2 moles of copper is present.
So mass of 0.2 moles of copper = = 12.7 grams