1. Na3PO4+Mg(NO3)2= NaNO3 + MgPO4
So this is not the answer.
2. Al+CuCl2= AlCl3+ Cu
So this is the answer.
3. Mg+O2= MgO2
So this is not an answer
4. Cl2+KI= KCl+I2
So this is also an answer
Hence B and C are answers
Answer:
millions of years sometimes even hundred of millions of years
Answer :
The concentration of
before any titrant added to our starting material is 0.200 M.
The pH based on this
ion concentration is 0.698
Explanation :
First we have to calculate the concentration of
before any titrant is added to our starting material.
As we are given:
Concentration of HBr = 0.200 M
As we know that the HBr is a strong acid that dissociates complete to give hydrogen ion
and bromide ion
.
As, 1 M of HBr dissociates to give 1 M of 
So, 0.200 M of HBr dissociates to give 0.200 M of 
Thus, the concentration of
before any titrant added to our starting material is 0.200 M.
Now we have to calculate the pH based on this
ion concentration.
pH : It is defined as the negative logarithm of hydrogen ion concentration.
![pH=-\log [H^+]](https://tex.z-dn.net/?f=pH%3D-%5Clog%20%5BH%5E%2B%5D)


Thus, the pH based on this
ion concentration is 0.698
Answer: D
Explanation:
They form from Coal under high high pressure and many many years