Question 1

Which law states that in a chemical reaction, matter is neither created nor destroyed, and who formulated this law?

Accepted Answer

Law of Conservation of Mass, Antoine Lavoisier

Question 2

According to Dalton’s atomic theory, which statement is FALSE?

Accepted Answer

Atoms can be divided into smaller particles and still retain the properties of the element.

Question 3

Which experiment led to the discovery of the electron, and what was the key observation?

Accepted Answer

Thomson’s cathode ray experiment; observed rays bending toward positive plates

Question 4

Which of the following best describes the plum-pudding model of the atom?

Accepted Answer

Electrons are embedded in a positively charged sphere.

Question 5

Rutherford’s gold foil experiment disproved the plum-pudding model. What was the main evidence?

Accepted Answer

Some alpha particles were deflected at large angles, indicating a dense nucleus.

Question 6

Which subatomic particle has no electrical charge and a mass similar to that of a proton?

Accepted Answer

Neutron

Question 7

What is the atomic number ($$Z) of an $$element, and how is it determined?

Accepted Answer

The number of protons in the nucleus

Question 8

Which group of elements is characterized by being mostly unreactive and having full electron shells?

Accepted Answer

Noble gases

Question 9

An atom of chlorine has an atomic mass of 35.45 amu. What is the mass of one mole of chlorine atoms?

Accepted Answer

$$35.45\ 	ext{g}$$

Question 10

Which element is a metalloid and exhibits properties intermediate between metals and nonmetals?

Accepted Answer

Silicon

Question 11

How many atoms are in $$75.0\ 	ext{g} of $$mercury ($$	ext{Hg}$$)? (Atomic mass of Hg = $$200.59\ 	ext{g/mol}$$, Avogadro’s number $$= 6.02 	imes 10$$^{23}$$)

Accepted Answer

$$2.25 	imes 10$$^{23}$$

Question 12

Which law explains why the ratio of oxygen to hydrogen in water is always the same, regardless of the sample?

Accepted Answer

Law of Definite Proportions

Question 13

What is the average atomic mass of silicon given the following data: Silicon-28 ($$27.9769\ 	ext{amu}$$, $$92.28\%$$), Silicon-29 ($$28.9765\ 	ext{amu}$$, $$4.70\%$$), Silicon-30 ($$29.9738\ 	ext{amu}$$, $$3.02\%$$)?

Accepted Answer

$$28.09\ 	ext{amu}$$

Question 14

Which statement about isotopes is correct?

Accepted Answer

Isotopes have the same atomic number but different mass numbers.

Question 15

Which element is most likely to form a cation during a chemical reaction?

Accepted Answer

Sodium

Question 16

Which property is NOT characteristic of metals?

Accepted Answer

Gain electrons during chemical changes

Question 17

What is the molar mass ($$M_m) of $$sodium chloride ($$	ext{NaCl}$$)? (Atomic masses: Na = $$22.99\ 	ext{g/mol}$$, Cl = $$35.45\ 	ext{g/mol})$$

Accepted Answer

$$58.44\ 	ext{g/mol}$$

Question 18

Which group contains elements that are very reactive nonmetals and includes fluorine and chlorine?

Accepted Answer

Halogens

Question 19

If an atom has 6 protons, 8 neutrons, and 6 electrons, what is its mass number?

Accepted Answer

$$14$$

Atoms and Elements: Foundations of Modern Chemistry

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