Explanation:
a) Using Beer-Lambert's law :
Formula used :

where,
A = absorbance of solution = 0.945
c = concentration of solution = ?
l = length of the cell = 1.20 cm
= molar absorptivity of this solution =


(
)
14.16 μM is the molarity of the red dye solution at the optimal wavelength 519nm and absorbance value 0.945.
b) 
1 L of solution contains
moles of red dye.
Mass of
moles of red dye:



c) In order to dilute red dye solution by 5 times, we will need to add 1 L of water to solution of given concentration.
Concentration of red dye solution = 
Concentration of red solution after dilution = c'



The final concentration of the diluted solution is 
Answer : 12 karat
Explanation : When pure gold is considered to be 24 karat then if its 50 mol% silver and 50 mol% silver then using karat scale calculation;
Karat/24 X 100 = 50 mol% (for gold) in alloy
So, Karat = (50 X 24) / 100 = 12 karat.
Hence the alloy will be of 12 karat.
Density= mass/ volume
So density = 99/10= 9.9g/cm^3
Hope this helps!! xx
Answer:
Mass: 981.0 g
Density: 5.61 g/cm^3
Hardness: = 2.5 - 3
Unknown material: Chalcocite