Question 1

Which of the following best describes the difference between a scientific law and a scientific theory?

Accepted Answer

A scientific law is a summary of observed phenomena, while a scientific theory provides an explanation for those phenomena.

Question 2

A student measures the mass of a metal sample as $$12.34\ \mathrm{g}$$, $$12.36\ \mathrm{g}$$, and $$12.35\ \mathrm{g} in $$three trials. The true mass is $$12.80\ \mathrm{g}. $$Which statement best describes the measurements?

Accepted Answer

The measurements are precise but not accurate.

Question 3

Which of the following is an example of a heterogeneous mixture?

Accepted Answer

Salad with lettuce, tomatoes, and cucumbers

Question 4

Which of the following statements correctly distinguishes between an atom and a molecule?

Accepted Answer

An atom is a single particle of an element, while a molecule consists of two or more atoms bonded together.

Question 5

Which of the following best describes the motion and arrangement of particles in a liquid?

Accepted Answer

Particles are close together but can move past one another, allowing the liquid to flow.

Question 6

Which of the following is a chemical change?

Accepted Answer

Burning wood

Question 7

A graduated cylinder contains $$25.0\ \mathrm{mL} of $$water. After a metal object is submerged, the water level rises to $$32.5\ \mathrm{mL}. If $$the mass of the metal is $$60.0\ \mathrm{g}$$, what is its density?

Accepted Answer

$$2.40\ \mathrm{g/mL}$$

Question 8

Convert $$4.56 	imes 10^3$ to ordinary decimal notation.

Accepted Answer

$$4560$$

Question 9

A sample has a mass of $$250\ \mathrm{mg}. $$What is this mass in grams?

Accepted Answer

$$0.25\ \mathrm{g}$$

Question 10

A block of wood has a density of $$0.85\ \mathrm{g/cm^3$}. $$Will it float or sink in water, and why?

Accepted Answer

It will float because its density is less than water.

Question 11

Which of the following best describes the law of definite proportions?

Accepted Answer

A compound always contains the same elements in the same proportion by mass.

Question 12

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

Accepted Answer

Thomson's cathode ray experiment; cathode rays were deflected by electric and magnetic fields.

Question 13

Which subatomic particle has the least mass?

Accepted Answer

Electron

Question 14

An atom has an atomic number $$Z = 17$$ and a mass number $$A = 37. $$How many neutrons does it have?

Accepted Answer

$$20$$

Question 15

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 16

Given the following isotopes of magnesium: $$^{24}\mathrm{Mg} (78.99$$%, mass = 23.985 amu), $$^{25}\mathrm{Mg} (10.00$$%, mass = 24.986 amu), and $$^{26}\mathrm{Mg} (11.01$$%, mass = 25.983 amu), what is the average atomic mass of magnesium? (Round to two decimal places.)

Accepted Answer

$$24.31\ \mathrm{amu}$$

Question 17

A chemical reaction starts with $$10.0\ \mathrm{g} of $$reactant A and $$15.0\ \mathrm{g} of $$reactant B. If the only product is compound C, what is the mass of compound C formed according to the law of conservation of mass?

Accepted Answer

$$25.0\ \mathrm{g}$$

Question 18

Which of the following best explains why Rutherford's gold foil experiment disproved the plum pudding model?

Accepted Answer

It revealed that most of the atom is empty space with a small, dense, positively charged nucleus.

Question 19

A student needs to convert $$5.00\ \mathrm{km} to $$nanometers ($$\mathrm{nm}). $$What is the correct value?

Accepted Answer

$$5.00 	imes 10$$^{12}$$\ \mathrm{nm}$$

Question 20

Which of the following is the correct symbolic notation for an isotope of carbon with 7 neutrons?

Accepted Answer

$$^{13}_{6}\mathrm{C}$$

General Chemistry: Foundations, Measurement, and Atomic Structure

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