Question

Calculate the oxidation number of metals in the following co-ordination compounds. 1) [Cr(NH3)(NO3)3] 2) [Ni(NH3)6]Cl2 3) K3[Al(C2O4)3]

Answer 1

Answer:

Let, speed of Ritu in still water be x km/hr

and speed of current be y km/hr

Then speed downstream =(x+y) km/hr

speed upstream =(x−y) km/hr

we know, Time=

Speed

Distance

Then

x+y

20

=2 and

x−y

4

=2

⇒x+y=10 ...(1)

& x−y=2 ...(2)

adding both we get, 2x=12⇒x=6

Thus using (1) y=10−6=4

Hence the speed of Ritu in still water is 6 km/hr and the speed of the current is 4 km/hr.

Answer 2

Explanation:

To Find -

• Oxidation number of metal in all compounds.

1)

[Cr(NH3)6(NO3)3]

Here, we need to find the O.N. of Cr.

Let x be the O.N. of Cr

Then,

→ x + 0×6 - 1×3 = 0

→ x = +3

2)

[Ni(NH3)6]Cl2

Here, we need to find the O.N. of Ni.

Let x be the O.N. of Ni

Then,

→ x + 0×6 - 1×2 = 0

→ x = + 2

3)

K3[Al(ox)3]

Here, we need to find the O.N. of Al.

Let x be O.N. of Al

Then,

→ 1×3 + x - 2×3 = 0

→ x = +3

Additional information :-

Oxidation number :-

• It's a hypothetical number calculated on the basis of certain rules, assuming all the compounds to be ionic.

Rules :-

1. O.N. of any element in its free state is 0
2. O.N. of Li, Na, K, Rb, Cs, Fr = +1
3. O.N. of Be, Mg, Ca, Sr, Ba, Ra = +2
4. O.N. of F, CL, Br, I = -1
5. O.N. of H is generally +1, but in metal hydrides it's -1
6. O.N. of Oxygen is generally -2 (oxide), But in peroxide it's -1 and in superoxide it's -½.
7. O.N. of any ion is equal to its charge.
8. Sum of O.N. of all the atoms of a molecule is zero.