Explanation:
The given data is as follows.
= 211 nm, 
l = 1 cm, 7% < Transmittance < 85%
Suppose the aqueous solution follows Lambert-Beer's law. Therefore,
Absorbance = 
Hence, for 7% transmittance the value of absorbance will be as follows.
Absorbance = 
= 1.155
For 85% transmittance the value of absorbance will be as follows.
Absorbance = 
= 0.07058
According to Lambert-Beer's law.
A = 
where, A = absorbance
= molar extinction coefficient
C = concentration
Therefore, concentration for 7% absorbance is as follows.

= 
= 
= 0.187 mmol/L
Concentration for 85% absorbance is as follows.

= 
= 
= 0.01144 mmol/L
Thus, we can conclude that linear range of phenol concentration is 0.01144 mmol/L to 0.187 mmol/L.
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In the lake that the rivers lead, water molecules evaporate into the sky and form clouds. In the sky, these water droplets condense and form clouds that will eventually rain.
According to the balanced equation of the reaction:
2C2H2 + 5O2 → 4CO2 + 2H2O
So we can mention all as liters,
A) as we see that 2 liters of C2H2 react with 5 liters of oxygen to produce 4 liters of CO4 and 2 liters of H2O
So, when we have 75L of CO2
and when we have 2 L of C2H2 reacts and gives 4 L of CO2
2C2H2 → 4CO2
∴ The volume of C2H2 required is:
= 75L / 2
= 37.5 L
B) and, when we have 75 L of CO2
and 4CO2 → 2H2O
∴ the volume of H2O required is:
= 75 L /2
= 37.5 L
C) and from the balanced equation and by the same way:
when 5 liters O2 reacts to give 4 liters of CO2
and we have 75 L of CO2:
5 O2 → 4 CO2
?? ← 75 L
∴ the volume of O2 required is:
= 75 *(5/4)
= 93.75 L
D) about the using of the number of moles the answer is:
no, there is no need to find the number of moles as we called everything in the balanced equation by liters and use it as a liter unit to get the volume, without the need to get the number of moles.