The density of an ordinay rock is close to 3 g/cm^3 wihle the density of the paper clips is close to 8 g/cm^3 (the density of steel), then equal apparent volumes (same box) will contain different mass, being of course the mass of the box with paper clips much higher than that of the box with rocks.
Whether water is frozen, in a gaseous state, or is a liquid, it is still H2O. So the chemical composition does stay the same.
Answer: (a) The solubility of CuCl in pure water is 
.
(b) The solubility of CuCl in 0.1 M NaCl is 
.
Explanation:
(a) Chemical equation for the given reaction in pure water is as follows.
Initial: 0 0
Change: +x +x
Equilibm: x x
And, equilibrium expression is as follows.
![K_{sp} = [Cu^{+}][Cl^{-}]](https://tex.z-dn.net/?f=K_%7Bsp%7D%20%3D%20%5BCu%5E%7B%2B%7D%5D%5BCl%5E%7B-%7D%5D)
x =
Hence, the solubility of CuCl in pure water is .
(b) When NaCl is 0.1 M,
,
, 
Net equation: 
= 0.1044
So for,
Initial: 0.1 0
Change: -x +x
Equilibm: 0.1 - x x
Now, the equilibrium expression is as follows.
K' = 
0.1044 = 
x =
Therefore, the solubility of CuCl in 0.1 M NaCl is .
<span>H2CO3 <---> H+ + HCO3-
NaHCO3 <---> Na+ + HCO3-
When acid is added in the buffer, the excess H+ of that acid reacts with HCO3- to form H2CO3, and due to this NaHCO3 dissociates into HCO3- to attain the equilibrium. and hence there is no net effect of H+ due to pH remain almost constant.
when a base is added to the buffer, the OH- ion of base react eith H+ ion present in buffer, then to attain equilibrium of H+ ion, the H2CO3 dissociates to produce H+ ion, but now there is the excess of HCO3- due to which Na+ ion react with them to attain equilibrium of HCO3-. hence there is again no net change in H+ ion due to which pH remain constant.....</span>
