Answer:
the value of molar absorptivity is 229000 
Explanation:
given data
phenol phthalein solution = 0.050 g
total volume = 100.0 ml
dilute = 100.0 ml
diluted sample = 0.18
solution
we get here concentration that is express as
concentration = ( mass of solute × 1000 ) ÷ ( molar mass of solute × volume of solution ) .............1
put here value
concentration =
concentration = 0.00157 M
and here dillution equation is express as
c1 × v1 = c2 × v2 .................2
here c1 and c2 is initial and final concentration
and v1 and v2 is initial and final volume
put here value
0.001571 × 0.050 = c2 × 100
c2 = 7.855 ×
M
and
now we get molar by absorbance equation that is
A = E × C × l ................3
here A is absorbance and E is molar and c is absorptivity and l is path length
put here value
0.18 = E × 7.855 ×
× 1
E = 229000 
Knowing that 1 mL = 1000 uL , you just multiply by 1000
The atoms of chlorine are held together by non-polar covalent bonds. Covalent bonds are formed between two or more atoms having zero or very small electronegativity difference. For homonuclear molecules where the two bonding atom are of the same kind, the electronegativity difference is zero.
The answer is pH = 7.37.
Solution:
First, we set up an ICE table for the reaction:
F- + H2O → HF + OH-
Initial 0.00378 0 0
Change -x +x +x
Equilibrium 0.00378-x x x
We can calculate Kb from the given Ka, since we know that Kw = Ka*Kb = 1.0 x 10^-14 at 25°C:
Kb = Kw/Ka = 1.0x10^-14 / 6.80x10^-4 = 1.471 x 10^-11
Kb = 1.471 x 10^-11 = [OH-][HF] / [F-] = (x)(x) / (0.00378-x)
Approximating that x is negligible compared to 0.00378 simplifies the equation to
1.471x10^-11 = (x)(x) / 0.00378
1.471 x 10-11 = x2 / 0.00378
Then we solve for x that is also equal to [OH-]:
x2 = (1.471 x 10^-11)(0.00378)
x = sqrt[(1.471 x 10^-11)(0.00378)] = 2.358x10^-7 = [OH-]
in which 0.0000002358 is indeed negligible compared to 0.00378.
We can now calculate for pOH:
pOH = -log [OH-] = -log (2.358x10^-7) = 6.63
Therefore, the pH is
pH = 14 - pOH = 14 - 6.63 = 7.37