Earthquakes along the San Andreas fault in California.
<u>Explanation</u>:
- When the two plates collide with each other, earthquakes occur. The contact between them makes this earthquake possible. The contact forces are responsible for the earthquakes as there is contact between two plates.
- The gravitational force is a force that is responsible for elevated tides happening on the east coast or the Jupiter's moons to remain in orbit. But this is not a contact force as there is no contact between them
- Moreover, Without any contact, the magnetic force is a non-contact as it attracts the pins from a distance.
[Co(NH₃)₅Br]²⁺
Ligands and charges on them,
5 × NH₃ = 5 × 0 = 0
1 × Br⁻¹ = 1 × -1 = -1
Charge on sphere = +2
So, putting values in equation,
Co + (0)₅ - 1 = +2
Co + 0 - 1 = +2
Co - 1 = +2
Co = +2 + 1
Co = +3
Result:
Oxidation state of Co in [Co(NH₃)₅Br]²⁺ is +3.

If every oxygen ion is combined with an aluminium ion has a charge of -2,the charge of each aluminum ion would be -3.
Uncharged Aluminum atom must need to lose it's electrons,in order to form the bond with oxygen which has vacant orbitals
ion
atom that has a positive or negative charge because it lost or gained one or more electrons
chemical bond
the attractive force that holds atoms or ions together
ionic bond
a chemical bond in which one atom loses an electron and the other atom gains electrons to form ions
chemical formula
a combination of chemical symbols and numbers to represent a substance
covalent bond
bond formed by the sharing of electrons between atoms
n=20 mol
(NH)4 SO4
Atomic masses :
N- 14
H- 1
S- 32
O- 16
Therefore M= 14×2 + 1×8 + 32 + 16×4
= 132
m= nM
= 20×132
= 2640g