1) What is the objective of this experiment? (name of the experiment Beer\'s Law

Question

1) What is the objective of this experiment? (name of the experiment Beer's Law)

A) to create a calibration curve and solve for an unknown concentration of an element.

B) to introduce Beer's Law.

C) All are correct.

D) To illustrate the principles of emission and absorption.

2) Which of the following is NOT correct regarding electromagnetic radiation?

A) The energy of light is directly proportional to the frequency.

B) Longer wavelengths equal larger energies.

C) The speed of light is a constant number: 3 x 10^8 m/sec.

D) The speed of light equals the product of wavelength and Frequency.

3) Which of the following is NOT correct regarding the Bohr model of the atom?

A) It is a good model for the hydrogen atom but has shortcomings with more complex atoms.

B) When electrons absorb light, they are excited into the outter electron orbitals.

C) It is also called the 'planetary model'.

D) Electrons in interior orbitals have a higher energy and those in the outter orbitals have lower energy.

4) What is the molarity of a solution if 0.1846 moles of a chemical is dissolved in 379-mL of water?

5) Which of the following is NOT correct regarding Beer's Law?

A) As the concentration of a solution increases, the absorption of light increases.

B) Absorbance is directly proportional to concentration.

C) At high concentration, absorption and concentration do not have a linear relationship.

D) The molar absorptivity constant varies with the concentration of the solution

Explanation / Answer

1)

beers law is A = e x l x c

so

the objective is to create a calibration curve and solve for an unknown concentration of an element

also

to illustrate the principles of emission and absorption

so

the answer is C) All are correct

2)

we know that

for a electromagnetic radiation

E = h x f

frequency (f) = speed of light (c) / wavelength (lamda)

c = speed of light = 3 x 10^8 m/s

E = h x c / lamda

so

longer wavelengths equal smaller energies

so

the answer is

B) longer wavelengths equal larger energies

3)

yes it is also called planetary model

yes when electrons absorb light, they are excited into the outter electron orbitals

it is most suitable for hydrogen atom

finally

electrons in the outermost orbitals have higher energy than electrons in interior orbitals

so

the wrong statement is

D) Electrons in interior orbitals have a higher energy and those in the outter orbitals have lower energy

4)

we know that

molarity = moles x 1000 / volume (ml)

given

moles = 0.1846

volume (ml) = 379

so

molarity = 0.1846 x 1000 / 379

molarity = 0.487

so

molarity of the solution is 0.487

5)

we know that

according to Beers law

A = e x l x c

we can see that

abosorbance is directly proportional to concentration

so

as the conc increases , the absorption of light increases

also

at high concentration, absorption and concentration do not have a linear relationship

now

the molar abosorptivity constant is a constant

and it only depends on the material used not the concentration

so

the given statement is wrong

so

the answer is

D) The molar absorptivity constant varies with the concentration of the solution

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