Q: Which of the following is the correct formula for calculating the average atomic mass of an element with two isotopes?

$$\text{Average atomic mass} = (\text{fraction of isotope 1}) \times (\text{mass of isotope 1}) + (\text{fraction of isotope 2}) \times (\text{mass of isotope 2})$$

Q: A sample contains 12.01 g of carbon. How many atoms of carbon are present in the sample? (Atomic mass of C = 12.01 g/mol)

$$6.022 \times 10$$^{23}$$ atoms

Question 1

Which experiment provided the first direct evidence for the existence of the atomic nucleus?

Accepted Answer

Rutherford's gold foil experiment

Question 2

According to Dalton's atomic theory, which statement is correct?

Accepted Answer

Atoms combine in simple whole-number ratios to form compounds.

Question 3

A sample of carbon dioxide contains 2.67 g of oxygen per 1 g of carbon, while carbon monoxide contains 1.33 g of oxygen per 1 g of carbon. What law does this observation illustrate?

Accepted Answer

Law of Multiple Proportions

Question 4

Which of the following statements about isotopes is TRUE?

Accepted Answer

Isotopes of an element have different numbers of neutrons.

Question 5

Which of the following best describes the result of Rutherford's gold foil experiment?

Accepted Answer

Most alpha particles passed straight through, but some were deflected at large angles.

Question 6

Which property is NOT characteristic of metals?

Accepted Answer

Tends to gain electrons in chemical reactions

Question 7

A neutral atom of magnesium has an atomic number of 12 and a mass number of 24. How many neutrons does it have?

Accepted Answer

12

Question 8

Which group in the periodic table contains elements that are generally unreactive and exist as gases at room temperature?

Accepted Answer

Noble gases

Question 9

Which of the following is the correct formula for calculating the average atomic mass of an element with two isotopes?

Accepted Answer

$$	ext{Average atomic mass} = (	ext{fraction of isotope 1}) 	imes (	ext{mass of isotope 1}) + (	ext{fraction of isotope 2}) 	imes (	ext{mass of isotope 2})$$

Question 10

Which of the following statements about the mole is correct?

Accepted Answer

A mole is 6.022 x $$10^{23}$$ particles of a substance.

Question 11

A sample contains 12.01 g of carbon. How many atoms of carbon are present in the sample? (Atomic mass of C = 12.01 g/mol)

Accepted Answer

$$6.022 	imes 10$$^{23}$$ atoms

Question 12

Which of the following elements is a metalloid and commonly used as a semiconductor in electronics?

Accepted Answer

Silicon

Question 13

Which of the following ions is most likely to be formed by a main-group nonmetal?

Accepted Answer

An anion with the same number of electrons as the nearest noble gas

Question 14

Which of the following best explains why most of the mass of an atom is concentrated in the nucleus?

Accepted Answer

The nucleus contains protons and neutrons, which are much heavier than electrons.

Question 15

A student is given a 4.00 g sample of helium (atomic mass = 4.00 g/mol). How many atoms of helium are in the sample?

Accepted Answer

$$6.022 	imes 10$$^{23}$$ atoms

Question 16

Which of the following best describes the charge and mass of a neutron?

Accepted Answer

Charge: 0, Mass: approximately 1 amu

Question 17

Which of the following is a correct conversion factor for converting moles of atoms to number of atoms?

Accepted Answer

$$6.022 	imes 10$$^{23}$$ 	ext{ atoms} / 1 	ext{ mol}$$

Question 18

Which of the following best describes the difference between a period and a group in the periodic table?

Accepted Answer

A period is a horizontal row; a group is a vertical column.

Question 19

A student finds a sample of an unknown element. It is shiny, conducts electricity, and can be drawn into wires. To which class of elements does it most likely belong?

Accepted Answer

Metals

Question 20

Which of the following best explains why the chemistry of different isotopes of an element is nearly identical?

Accepted Answer

Isotopes have the same number of protons and electrons, which determine chemical behavior.

Atoms and Elements: Foundations of Atomic Theory and the Periodic Table

Guida di studio - Domande di pratica

Study guide - Flashcard