Q: Calculate the atomic mass of chlorine given 75.77% $$^{35}Cl ($$mass = 34.97 amu) and 24.23% $$^{37}Cl ($$mass = 36.97 amu).

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

Question 1

Which of the following best describes a compound?

Accepted Answer

A substance composed of two or more elements in fixed, definite proportions.

Question 2

Which of the following statements about the law of conservation of mass is correct?

Accepted Answer

In a chemical reaction, matter is neither created nor destroyed.

Question 3

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

Accepted Answer

$$\frac{16.0}{2.0} = 8.0$$

Question 4

Which of the following is a heterogeneous mixture?

Accepted Answer

A mixture of sand and salt

Question 5

Which experiment led to the discovery of the electron?

Accepted Answer

J.J. Thomson’s cathode ray experiment

Question 6

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

Accepted Answer

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

Question 7

Which statement best explains the difference between a law and a theory?

Accepted Answer

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

Question 8

Which of the following is true about isotopes?

Accepted Answer

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

Question 9

Calculate the number of moles in a 35.8-gram pure copper sheet. (Molar mass of Cu = 63.55 g/mol)

Accepted Answer

$$\frac{35.8}{63.55} = 0.564$$ moles

Question 10

Which sample contains the most atoms: 1 g of copper, 1 g of carbon, or 1 g of uranium?

Accepted Answer

1 g of carbon

Question 11

A titanium cube contains $$2.15 	imes 10$$^{23}$$ atoms. The density of titanium is 4.50$$ 	ext{ g/cm}^3$$ and its molar mass is 47.87$$ 	ext{ g/mol}$$. What is the edge length of the cube in centimeters? (Avogadro’s number = 6.022$$ 	imes $$10^{23})$$

Accepted Answer

$$0.500 cm$$

Question 12

Which of the following best describes the nuclear model of the atom proposed by Rutherford?

Accepted Answer

Most of the atom’s mass and all of its positive charge are contained in a small core called a nucleus.

Question 13

Which law states that all samples of a given compound have the same proportions of their constituent elements?

Accepted Answer

Law of definite proportions

Question 14

A neutral atom of nitrogen has 7 protons and 7 neutrons. How many electrons does the $$\mathrm{N}^{3-}$$ ion have?

Accepted Answer

10

Question 15

Which of the following is a correct application of the law of multiple proportions?

Accepted Answer

The ratio of the masses of oxygen that combine with 1 g of carbon in CO and CO$$_2 is a $$small whole number.

Question 16

Which of the following is NOT a characteristic of a scientific hypothesis?

Accepted Answer

It is a brief statement that summarizes past observations and predicts future ones.

Question 17

Calculate the atomic mass of chlorine given 75.77% $$^{35}Cl ($$mass = 34.97 amu) and 24.23% $$^{37}Cl ($$mass = 36.97 amu).

Accepted Answer

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

Question 18

Which of the following is a property of gaseous matter?

Accepted Answer

Atoms or molecules have a lot of space between them and are compressible.

Question 19

Which of the following best describes a homogeneous mixture?

Accepted Answer

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

Atoms: The Building Blocks of Matter – Study Notes

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