Q: A platinum ring has a mass of 10.5 grams. Given that the atomic mass of platinum is $$195.08\ \mathrm{g/mol}$$, how many platinum atoms are in the ring? ($$N_A = 6.022 \times 10$$^{23}$$\ \mathrm{mol}^{-1})$$

$$3.24 \times 10$$^{22}$$ atoms

Question 1

Which law states that matter is neither created nor destroyed in a chemical reaction, and who is credited with its discovery?

Accepted Answer

Law of Conservation of Mass; Antoine Lavoisier

Question 2

A radioactive isotope of iodine is used in thyroid imaging. Which property of the thyroid gland allows this technique to work effectively?

Accepted Answer

The thyroid's ability to concentrate iodine

Question 3

Which instrument allows scientists to visualize the surface contours of atoms, such as those in a silicon chip?

Accepted Answer

Scanning tunneling microscope

Question 4

Which atomic model is depicted by a sphere of positive charge with electrons embedded throughout, and who proposed it?

Accepted Answer

Plum pudding model; J.J. Thomson

Question 5

Which of the following statements is consistent with Rutherford's nuclear theory?

Accepted Answer

The volume of an atom is mostly empty space.

Question 6

A sample of magnesium contains three isotopes: $$^{24}\mathrm{Mg} (78.99$$%, 23.9850 amu), $$^{25}\mathrm{Mg} (10.00$$%, 24.9858 amu), and $$^{26}\mathrm{Mg} (11.01$$%, 25.9826 amu). Calculate the atomic mass of magnesium.

Accepted Answer

$$24.31\ \mathrm{amu}$$

Question 7

Which of the following best explains why the atomic mass of chlorine (35.45 amu) does not match the mass of any single chlorine isotope?

Accepted Answer

Chlorine exists as a mixture of isotopes, and the atomic mass is a weighted average.

Question 8

A platinum ring has a mass of 10.5 grams. Given that the atomic mass of platinum is $$195.08\ \mathrm{g/mol}$$, how many platinum atoms are in the ring? ($$N_A = 6.022 	imes 10$$^{23}$$\ \mathrm{mol}^{-1})$$

Accepted Answer

$$3.24 	imes 10$$^{22}$$ atoms

Question 9

Which pair of elements would you expect to have the most similar chemical properties, and why?

Accepted Answer

Cl and F, because they are in the same group

Question 10

Which of the following ions has 34 protons and 36 electrons?

Accepted Answer

$$\mathrm{Se}^{2-}$$

Question 11

A diamond contains $$4.00 	imes 10$$^{24}$$ atoms of carbon. What is the mass of carbon in the diamond? (Molar mass of C = 12.01$$\ \mathrm{g/mol}$$, N_A = 6.022$$ 	imes $$10^{23}$$\ \mathrm{mol}^{-1}$$)

Accepted Answer

$$79.8\ \mathrm{g}$$

Question 12

Which statement about subatomic particles is FALSE?

Accepted Answer

Protons and neutrons have charges of the same magnitude but opposite signs.

Question 13

Which element is classified as a metalloid?

Accepted Answer

Tellurium

Question 14

Which of the following best describes the difference between isotopes of an element?

Accepted Answer

Isotopes have the same number of protons but different numbers of neutrons.

Question 15

How many electrons does it take to equal the mass of a proton? (Mass of proton $$= 1.67 	imes 10$$^{-24}$$\ \mathrm{g}$$, mass of electron $$= 9.11 	imes 10$$^{-28}$$\ \mathrm{g})$$

Accepted Answer

$$1.83 	imes 10$$^{3}$$

Question 16

Which of the following is the correct isotopic symbol for the hydrogen isotope with two neutrons?

Accepted Answer

H-3

Question 17

A sample of sodium fluoride produces 45.1 g of sodium upon decomposition. If the mass ratio of sodium to fluorine in sodium fluoride is $$1.21:1$$, how much fluorine (in g) forms?

Accepted Answer

$$37.3\ \mathrm{g}$$

Question 18

Which of the following elements is a main-group element?

Accepted Answer

Potassium

Question 19

Which of the following ions has 26 protons and 24 electrons?

Accepted Answer

$$\mathrm{Fe}^{2+}$$

Question 20

Which of the following best describes the process by which radioactive iodine is used to treat thyroid cancer?

Accepted Answer

Radioactive iodine accumulates in thyroid cells, emitting particles that either kill the cells or allow them to be imaged.

Atoms and Elements: Structure, Isotopes, and the Periodic Table

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