Question

13. Linear regression analysis was performed for a standard addition data set based on this experiment. The analysis yielded the following results: m = 0.006110, b = 0.008170. What is the unknown's riboflavin concentration (ppm) in the standard addition solutions?

a) 2.0

b) 13.37

c) 1.337

d) 1.67

15. The riboflavin concentration in the unknown powder solution is 58.0 ppm. The total volume of the powder solution is 250.00 mL. What is the concentration in the tablet (mg ribo/tablet) if the mass of tablet = 0.6377 g and the mass of powder = 0.5085 g?

a) 18.2

b) 18.18

c) 17.46

d) 18.8

5. Riboflavin absorbs UV-visible light making the electrons in the molecule more energetic. As a result, the more energetic electrons move from the 'ground state' electronic energy level to higher electronic energy levels known as 'excited states’. Which of the following statements is NOT true regarding how the ‘excited state’ molecule loses energy and returns to the 'ground state'?

a) non-radiative losses via collisions with other molecules

b) non-radiative losses via phosphorescence

c) non-radiative losses via bond vibration and rotation within the molecule

d) radiative losses via fluorescence emission of light

Answer 1

13. Linear regression analysis was performed for a standard addition data set based on this experiment. The analysis yielded the following results: m = 0.006110, b = 0.008170. What is the unknown's riboflavin concentration (ppm) in the standard addition solutions?

a) 2.0

b) 13.37

c) 1.337

d) 1.67

solution :- using the value of the b and m we can find the concentration in the ppm as follows

concentration = b/ m

                        = 0.008170 / 0.006110

                        = 1.337

Therefore the answer is option C

15. The riboflavin concentration in the unknown powder solution is 58.0 ppm. The total volume of the powder solution is 250.00 mL. What is the concentration in the tablet (mg ribo/tablet) if the mass of tablet = 0.6377 g and the mass of powder = 0.5085 g?

a) 18.2

b) 18.18

c) 17.46

d) 18.8

Solution :-

Total volume is 250 ml = 0.250 L

Mass of powder = 0.5085 g

Mass of tablet = 0.6377 g

Using the ppm concentration we can find the mass of riboflavin in the 250 ml sample

58.0 ppm *(1 mg/1ppm) * 0.250 L = 14.5 mg

Now using the mass in mg in the powder we can find the mass of riboflavin in the tablet

14.5 mg * 0.6377 g / 0.5085 g = 18.18 mg/g

Therefore the mass of the riboflavin in the tablet is 18.18 mg/g

Hence the answer is option b

  

5. Riboflavin absorbs UV-visible light making the electrons in the molecule more energetic. As a result, the more energetic electrons move from the 'ground state' electronic energy level to higher electronic energy levels known as 'excited states’. Which of the following statements is NOT true regarding how the ‘excited state’ molecule loses energy and returns to the 'ground state'?

a) non-radiative losses via collisions with other molecules

b) non-radiative losses via phosphorescence

c) non-radiative losses via bond vibration and rotation within the molecule

d) radiative losses via fluorescence emission of light

Solution :- The energy absorbed by the molecules causes the electrons to increase in the energy and therefore the lower energy state electrons are transferred to excited state energy level of higher energies. So when the electrons from the higher energy try to come down to the lower energy states then they emits the energy in the form of the radiation.

Therefore the statement which is not true is the option b

Because phosphorescence is the loss of energy via radiation.