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? ($$1\ \mathrm{mol} = 6.022 \times 10$$^{23}$$ atoms)

$$3.24 \times 10$$^{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 of the following statements is consistent with Rutherford's nuclear theory?

Accepted Answer

The nucleus of an atom is small compared to the size of the atom.

Question 5

Which atomic model first introduced the concept of quantized orbits for electrons?

Accepted Answer

Bohr model

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 pair of elements would you expect to have the most similar chemical properties?

Accepted Answer

Cl and F

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? ($$1\ \mathrm{mol} = 6.022 	imes 10$$^{23}$$ atoms)

Accepted Answer

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

Question 9

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

Accepted Answer

$$^3\mathrm{H}$$

Question 10

Which law explains why two samples of sodium chloride, when decomposed, always produce sodium and chlorine in the same mass ratio?

Accepted Answer

Law of Definite Proportions

Question 11

How many moles of carbon are present in a diamond with a mass of $$0.800\ \mathrm{g}$$? (Molar mass of C = $$12.01\ \mathrm{g/mol})$$

Accepted Answer

$$0.0666\ \mathrm{mol}$$

Question 12

Which of the following statements about subatomic particles is FALSE?

Accepted Answer

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

Question 13

A sample of gold contains $$4.65 	imes 10$$^{24}$$ atoms. How many moles of gold does the sample contain? (1$$\ \mathrm{mol} = 6.022 	imes $$10^{23}$$ atoms)

Accepted Answer

$$7.72\ \mathrm{mol}$$

Question 14

Which element is classified as a metalloid?

Accepted Answer

Tellurium

Question 15

Which of the following ions has 28 protons and 26 electrons?

Accepted Answer

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

Question 16

Which pair of compounds best illustrates the law of multiple proportions?

Accepted Answer

CO and CO$$_2$$

Question 17

A student weighs out a 10.0-g sample of aluminum and a 10.0-g sample of copper. Which sample contains more atoms and why?

Accepted Answer

Aluminum, because it has a lower molar mass than copper.

Question 18

Which scientist is credited with organizing the periodic table based on atomic mass and chemical properties?

Accepted Answer

Dmitri Mendeleev

Question 19

Which isotope is used as a radiotracer in thyroid imaging and therapy?

Accepted Answer

$$^{131}\mathrm{I}$$

Question 20

Which of the following best describes the structure of sodium chloride (NaCl) in the solid state?

Accepted Answer

A lattice of alternating Na$$^+$$ and Cl$$^-$$ ions

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

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