Q: A hospital uses a radioactive isotope of iodine, $$^{131}\mathrm{I}$$, for thyroid imaging. If a sample contains $$6.02 \times 10$$^{20}$$ atoms of $$^{131}\mathrm{I}$$, how many moles of $$^{131}\mathrm{I}$$ are present?

$$1.00 \times 10$$^{-3}$$ moles

Question 1

Which experiment led to the discovery that the atom contains a small, dense, positively charged nucleus?

Accepted Answer

The gold foil experiment

Question 2

A hospital uses a radioactive isotope of iodine, $$^{131}\mathrm{I}$$, for thyroid imaging. If a sample contains $$6.02 	imes 10$$^{20}$$ atoms of $$^{131}\mathrm{I}$$, how many moles of $$^{131}\mathrm{I}$$ are present?

Accepted Answer

$$1.00 	imes 10$$^{-3}$$ moles

Question 3

Which of the following best explains why chlorine forms a $$1-$$ ion?

Accepted Answer

Chlorine gains one electron to achieve a noble gas electron configuration.

Question 4

A sample of magnesium contains $$1.20 	imes 10$$^{24}$$ atoms. What is the mass of this sample in grams? (Atomic mass of Mg = 24.31 g/mol)

Accepted Answer

$$48.6 g$$

Question 5

Which of the following statements about isotopes is correct?

Accepted Answer

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

Question 6

A neutral atom of calcium-40 ($$^{40}\mathrm{Ca}) $$has:

Accepted Answer

20 protons, 20 neutrons, and 20 electrons

Question 7

Which of the following elements is a metalloid?

Accepted Answer

Silicon

Question 8

A sample of a compound contains 12.0 g of carbon and 32.0 g of oxygen. According to the law of constant composition, what is the mass ratio of oxygen to carbon in this compound?

Accepted Answer

$$2.67:1$$

Question 9

Which of the following ions has the same number of electrons as a neutral argon atom?

Accepted Answer

$$\mathrm{Cl}^-$$

Question 10

A fictional element, X, has two naturally occurring isotopes: $$^{10}\mathrm{X} (20$$% abundance, mass = 10.0 amu) and $$^{11}\mathrm{X} (80$$% abundance, mass = 11.0 amu). What is the average atomic mass of element X?

Accepted Answer

$$10.8$$ amu

Question 11

Which of the following statements about the periodic table is TRUE?

Accepted Answer

Metals are generally found on the left side and in the middle of the periodic table.

Question 12

A sample contains $$3.01 	imes 10$$^{23}$$ atoms of gold. How many moles of gold are present?

Accepted Answer

$$0.500$$ moles

Question 13

Which of the following ions is isoelectronic with neon?

Accepted Answer

$$\mathrm{F}^-$$

Question 14

A student claims that all atoms of a given element must have the same mass. Which law or theory contradicts this claim?

Accepted Answer

The existence of isotopes

Question 15

If a neutral atom of phosphorus ($$\mathrm{P}) $$gains three electrons, what is the resulting ion's charge and electron count?

Accepted Answer

Charge: $$3-$$, Electrons: $$18$$

Question 16

Which of the following best describes the law of conservation of mass?

Accepted Answer

Matter cannot be created or destroyed in a chemical reaction.

Question 17

A sample of iron weighs 56.0 g. How many moles of iron does it contain? (Atomic mass of Fe = 55.85 g/mol)

Accepted Answer

$$1.00$$ mol

Question 18

Which of the following statements about the discovery of the electron is FALSE?

Accepted Answer

Rutherford proved the plum-pudding model correct.

Question 19

A sample of a compound contains 2.00 moles of hydrogen and 1.00 mole of oxygen. According to the law of constant composition, what is the empirical formula of this compound?

Accepted Answer

$$\mathrm{H}_2\mathrm{O}$$

Question 20

Which of the following elements is most likely to form a $$2+$$ ion?

Accepted Answer

Magnesium

Chapter 2 General Chemistry Study Guide – Step-by-Step Guidance

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