Q: A sample of pitchblende contains 71.4 g uranium and 12.8 g oxygen. If you have 142.8 g of pitchblende, how many grams of uranium would you expect to find?

$$142.8 \times \frac{71.4}{84.2} = 121.2 g$$

Q: A certain element has two naturally occurring isotopes: $$^{35}X ($$mass = 34.97 amu, abundance = 75.77%) and $$^{37}X ($$mass = 36.97 amu, abundance = 24.23%). What is the atomic mass of the element?

$$(0.7577 \times 34.97) + (0.2423 \times 36.97) = 35.45$$ amu

Question 1

Which of the following best describes the difference between a compound and a mixture?

Accepted Answer

A compound is composed of two or more elements chemically combined in fixed proportions, while a mixture consists of two or more substances physically intermingled in variable proportions.

Question 2

Which law is illustrated by the fact that 20.0 g of calcium carbonate always contains 8.0 g calcium, 2.4 g carbon, and 9.6 g oxygen, regardless of its source?

Accepted Answer

Law of Definite Composition

Question 3

A sample of pitchblende contains 71.4 g uranium and 12.8 g oxygen. If you have 142.8 g of pitchblende, how many grams of uranium would you expect to find?

Accepted Answer

$$142.8 	imes \frac{71.4}{84.2} = 121.2 g$$

Question 4

Which experiment provided evidence for the existence of a small, dense, positively charged nucleus in the atom?

Accepted Answer

Rutherford’s gold foil experiment

Question 5

Which of the following statements about isotopes is correct?

Accepted Answer

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

Question 6

A certain element has two naturally occurring isotopes: $$^{35}X ($$mass = 34.97 amu, abundance = 75.77%) and $$^{37}X ($$mass = 36.97 amu, abundance = 24.23%). What is the atomic mass of the element?

Accepted Answer

$$(0.7577 	imes 34.97) + (0.2423 	imes 36.97) = 35.45$$ amu

Question 7

Which of the following best describes a homogeneous mixture?

Accepted Answer

A mixture with a uniform composition throughout and no visible boundaries

Question 8

Which separation technique would be most effective for separating a mixture of sand and salt water?

Accepted Answer

Filtration

Question 9

Which of the following ions is most likely formed by an atom of magnesium?

Accepted Answer

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

Question 10

What is the correct name for the compound $$\mathrm{Fe}_2\mathrm{O}_3$$?

Accepted Answer

Iron(III) oxide

Question 11

Which of the following formulas represents a binary covalent compound?

Accepted Answer

$$\mathrm{CO}_2$$

Question 12

Which of the following is the correct systematic name for $$\mathrm{KNO}_2$$?

Accepted Answer

Potassium nitrite

Question 13

What is the formula for dinitrogen tetroxide?

Accepted Answer

$$\mathrm{N}_2\mathrm{O}_4$$

Question 14

Which of the following statements is NOT a postulate of Dalton’s atomic theory?

Accepted Answer

Atoms of one element can be converted into atoms of another element by chemical reactions.

Question 15

A sample contains only molecules made of two atoms of the same element. Which image best represents this sample?

Accepted Answer

Image B (yellow diatomic molecules)

Question 16

Which of the following is the correct formula for ammonium sulfate?

Accepted Answer

$$\mathrm{(NH}_4)_2\mathrm{SO}_4$$

Question 17

Which of the following best explains why the mass of substances does not change during a chemical reaction?

Accepted Answer

Atoms are rearranged but not created or destroyed.

Question 18

What is the molecular mass of $$\mathrm{P}_4\mathrm{S}_3$$? (Atomic masses: P = 30.97 amu, S = 32.06 amu)

Accepted Answer

$$(4 	imes 30.97) + (3 	imes 32.06) = 220.06$$ amu

Question 19

Which of the following is the correct name for $$\mathrm{H}_2\mathrm{SO}_3$$?

Accepted Answer

Sulfurous acid

Chapter 2: The Components of Matter – Structured Study Notes

Guida di studio - Domande di pratica

Study guide - Flashcard