Please I need help with these as soon as possible. a. molar absorptivity b. path

Question

Please I need help with these as soon as possible. a. molar absorptivity b. pathlength c, concentration d. temperature 2. If you mix sodium (Na) with water, a violent and exciting reaction will ensue producing hydrogen gas and sodium hydroxide. If you add 2.9 g of sodium to water and then add enough water to make l of solution. what is the molarity ofsodium in the resulting solution? 2Na +2H20 2NaoH H 2 3. A student measured the molar absorptivity of the copper to be uzlL mol 1 cm 1. She then measures the absorbance of the brass solution to be 0.21. What is the concentration of the copper in the brass solution if the nathlength (b) is 1.00 cm? 4. If you found the concentration of copper in the brass solution is 0.19, how many grams of copper are there in 5 of the brass solution?

Explanation / Answer

2. Mass of sodium = 2.9 g

Molar mass of sodium = 23 g/mol

Moles of sodium = Mass / Molar mass

= 2.9 / 23

= 0.126 moles

Volume of solution = 1 L

Molarity of solution = Moles of sodium / Volume of solution

= 0.126 / 1

= 0.126 M

3. Molar absorptivity, a = 1.71 L / mol-1 cm-1

Absorbance, A = 0.21

path length, b = 1.00 cm

Using Beer's law:

A = abc

0.21 = 1.71 * 1.00 * c

c = 0.21/ 1.71

c = 0.123 M

Hence, concentration = 0.123M

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