1. The isotope chromium-51 has a half-life of 28 days. If the original sample ha

Question

1. The isotope chromium-51 has a half-life of 28 days. If the original sample had a mass of 28.0 grams, what mass of the chromium-51 sample remains after 84 days?

a. 7.00 g

b. 3.50 g

c. 14.0 g

d. 1.00 g

2. A sample of thorium has an activity of 4,000 Bq. If the half-life of curium is 24.1 d, how long before its activity is 500 Bq?

a. 107.8 d

b. 94.5 d

c. 47.8 d

d. 85.7 d

e. 72.3 d

3. Consider the following reaction:

235 92 U --> 139 56 Ba + 94 36 Kr + 2 1 0N

Calculate the amount of energy given off by the reaction when 1 mole of uranium-235 undergoes this reaction.

a. 1.65 × 1010 kJ

b. 1.04× 106 kJ

c. 1.89× 103 kJ

d. 2.14× 10-10 kJ

e. 0.87× 10-2 kJ

4. In the symbol 168O, the number 16 indicates the _____ number of oxygen

5. A radioisotope decays to give an alpha particle and Pb-208 (daughter). What was the original (parent) element?

a. Hg

b. Rn

c. Bi

d. Se

e. Po

6. 1 Gy = _____

a. 100 J/g

b. 1000 J/g

c. 0.1 J/kg

d. 0.01 J/kg

e. 1 J/kg

7. The unit rem is defined as rem = rad × factor, where factor is a number less than or equal to 1 which accounts for the type of radioactivity.

a. True

b. False

8. Which molecule represented below is unsaturated?

a. C4H10

b. C3H8

c. CH4

d. CH3OH

e. C5H1

9. One of the functions of bile salts is to:

a. aid in the digestion of fats.

b. stimulate the conversion of proteins to carbohydrates.

c. prepare the uterus for pregnancy.

d. stimulate female sex characteristics.

e. maintaining kidney functions to retain sodium and excrete potassium.

10. Which of the following proteins performs the biological function of providing strength and structure?

a. Myosin

b. Ovalbumin

c. Hemoglobin

d. -Amylase

e. Keratin

11. What denaturation effect do alkaloid reagents have on proteins?

a. They engage in intermolecular hydrogen bonding with protein molecules, strengthening intramolecular hydrogen bonding within the protein.

b. They form strong bonds with the carboxylate anions of the acidic amino acids or SH groups of cysteine, disrupting ionic bonds and disulfide linkages.

c. They combine with positively charged amino groups in proteins and disrupt ionic bonds.

d. They cause protein atoms to vibrate more rapidly and crystallize the protein.

e. They supply kinetic energy to protein molecules and disrupt relatively strong hydrogen bonding and dispersion forces.

12. Erwin Chargaff of Columbia University is credited with developing the double-helix model for the secondary structure of DNA.

a. True

b. False

13. _____ is a heterocyclic amine with two nitrogen atoms in a six-member ring.

a. Pyrimidine

b. Adenosine

c. Purine

d. Pyridine

e. Uridine

14. Which of the following inorganic acids is obtained by breaking down nucleotides?

a. Sulfuric acid

b. Nitric acid

c. Phosphoric acid

d. Boric acid

e. Hydrochloric acid

Explanation / Answer

1)

we have:

Half life = 28 d

use relation between rate constant and half life of 1st order reaction

k = (ln 2) / k

= 0.693/(half life)

= 0.693/(28)

= 2.475*10^-2 d-1

we have:

[Cr]o = 28.0 g

t = 84.0 d

k = 2.475*10^-2 d-1

use integrated rate law for 1st order reaction

ln[Cr] = ln[Cr]o - k*t

ln[Cr] = ln(28) - 2.475*10^-2*84

ln[Cr] = 3.3322 - 2.475*10^-2*84

ln[Cr] = 1.2532

[Cr] = 3.50 g

Answer: b

Only 1 question at a time please

Related Questions

Navigate

• Browse (All)
• Browse 1
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.