Pakistan MCQs

Transition-metal chemistry arises from partially filled d orbitals.
Common features include variable oxidation states and colored ions.

Four oxygens contribute -8 total.
Sulfur must be +6 so the ion total is -2.

Potassium is +1 and four oxygens total -8.
Manganese must be +7 for a neutral compound.

Use E°cell=E°cathode-E°anode.
0.80-(-0.40)=1.20 V.

Oxygen is the most abundant element in Earth's crust by mass.
It occurs mainly in oxides and silicate minerals.

Aluminum is the most abundant crustal metal.
It is commonly found in aluminosilicate minerals and bauxite.

Alkali metals have one valence electron.
They usually lose it to form +1 ions.

Group 2 metals have two valence electrons.
They commonly lose both and form +2 ions.

Filled valence shells are especially stable.
Noble gases therefore have little tendency to gain or lose electrons.

Fluorine has very high electronegativity and a weak F-F bond.
It is the strongest elemental oxidizing halogen.

Allotropes differ in atomic arrangement and properties.
Diamond and graphite are carbon allotropes.

PH=-log(1×10^-3).
The result is 3.