Q: Calculate the atomic mass of chlorine given the following data: 75.77% chlorine-35 (mass = 34.97 amu) and 24.23% chlorine-37 (mass = 36.97 amu).

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

Question 1

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

Accepted Answer

A law summarizes a series of related observations, while a theory gives the underlying reasons for them.

Question 2

Which of the following is a pure substance?

Accepted Answer

Oxygen gas ($$\mathrm{O}_2)$$

Question 3

A sample of water decomposes to give 16.0 g of oxygen and 2.0 g of hydrogen. What is the mass ratio of oxygen to hydrogen in water?

Accepted Answer

$$8.0$$

Question 4

Which of the following best explains why gases are compressible?

Accepted Answer

Gases have atoms or molecules with a lot of space between them.

Question 5

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

Accepted Answer

Sand and iron filings

Question 6

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

Accepted Answer

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

Question 7

A chlorine isotope has 17 protons and 18 neutrons. What is its isotope symbol?

Accepted Answer

$$^{35}_{17}\mathrm{Cl}$$

Question 8

Which experiment led to the discovery of the electron?

Accepted Answer

Cathode ray tube experiment

Question 9

A neutral atom of nitrogen has an atomic number of 7. How many electrons does a $$\mathrm{N}^{3-}$$ ion have?

Accepted Answer

10

Question 10

Which of the following samples contains the most atoms?

Accepted Answer

A 1-g sample of carbon

Question 11

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

Accepted Answer

Law of conservation of mass

Question 12

A titanium cube contains $$2.15 	imes 10$$^{23}$$ atoms. The density of titanium is 4.50$$\ \mathrm{$$g/cm^3$$}$$. What is the first step to find the edge length of the cube?

Accepted Answer

Convert the number of atoms to moles using Avogadro’s number.

Question 13

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 14

Calculate the atomic mass of chlorine given the following data: 75.77% chlorine-35 (mass = 34.97 amu) and 24.23% chlorine-37 (mass = 36.97 amu).

Accepted Answer

$$(0.7577 	imes 34.97) + (0.2423 	imes 36.97) = 35.45\ \mathrm{amu}$$

Question 15

Which of the following best describes a homogeneous mixture?

Accepted Answer

A mixture that appears to be one substance with uniform composition throughout.

Question 16

Which statement is true regarding the size of isotopes of a given element?

Accepted Answer

For a given element, the size of an atom is the same for all the element’s isotopes.

Question 17

Which of the following is NOT a step in the scientific method?

Accepted Answer

Ignoring observations that do not fit the hypothesis

Question 18

A sample of carbon monoxide produces 17.2 g of oxygen and 12.9 g of carbon. Another sample produces 10.5 g of oxygen and 7.88 g of carbon. Are these results consistent with the law of definite proportions?

Accepted Answer

Yes, because the mass ratios are the same.

Question 19

Which of the following is the correct conversion factor for calculating the number of atoms in a given number of moles?

Accepted Answer

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

Atoms and the Structure of Matter: Chapter 1 Study Notes

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