Its doesn't dissolve in water!
Molarity of acid=2.5M
pH=5.1.
ka=?
Now
We need to write an eqn to show the dissociation of the acid
HA + H2O === H3O+ + A-
Writing The Equilibrium(Or Acid dissociation constant) of this reaction
Ka =[H3O+] {A-]/ {HA].
The concept behind this is
concentration of Products divided by those of reactants. Water is not written because its a pure liquid and does not affect the Equilibrium constant.
Now If you have any Idea on ICE tables..
You'd know that the concentration of acid will decrease by 2.5-x
Whilst the products...will increase by x each
Note: This is when the ratio of their Moles are in 1:1
ka= x.x/2.5-x
Since the Moles of A- and H3O+ are in 1:1... Their concentrations at equilibrium will be the same
so
Ka= x²/2.5-x
Now what is x??
x is the Hydrozonium ion concentration.
we can get it from the pH formula
pH= -log (H3O+)
Making H3O+ subject by applying Logarithm Rules
H3O+ = 10^-ph
x=10^-5.1
=7.94x10^-6.
Now back to Ka
Ka= x²/2.5-x
Ka= (7.94x10^-6)²/2.5-(7.94x10^-6)
Ka= (7.94x10^-6)²/2.4999
Ka= 2.52x10^-11.
Was a Fun One
The length, width and height of the wall of room is 12.0 ft, 15.0 ft and 9 ft respectively. To calculate the gallons of paint to paint the room with two coats, first calculate the surface area of room that needs to be coated.
The total surface are of room without ceiling will be:
![A=2(l\times h)+2(w\times h)](https://tex.z-dn.net/?f=A%3D2%28l%5Ctimes%20h%29%2B2%28w%5Ctimes%20h%29)
Here, l is length, h is height and w is width of the room.
Putting the values,
![A=2(12.0 ft\times 9 ft)+2(15.0 ft\times 9 ft)=486 ft^{2}](https://tex.z-dn.net/?f=A%3D2%2812.0%20ft%5Ctimes%209%20ft%29%2B2%2815.0%20ft%5Ctimes%209%20ft%29%3D486%20ft%5E%7B2%7D)
Since, 1 gallon of paint is used for area
, for
of area, volume of paint used will be 0.00267 gallon.
Thus, volume of paint used for area
will be:
![V=486 ft^{2}\times 0.00267gallon/ft^{2}\approx 1.3 gallon](https://tex.z-dn.net/?f=V%3D486%20ft%5E%7B2%7D%5Ctimes%200.00267gallon%2Fft%5E%7B2%7D%5Capprox%201.3%20gallon)
The above volume is for 1 coat of paint, for 2 coats volume will be:
![V=2\times 1.3=2.6 gallon](https://tex.z-dn.net/?f=V%3D2%5Ctimes%201.3%3D2.6%20gallon)
Therefore, paint required to paint room with two coats is 2.6 gallon.
1,200,000,000,000
Multiple 10 to the power of 11
10x10x10x10x10x10x10x10x10x10x10=100,000,000,000
Then multiply by 12