Chapter 3

Question 1

Sulfur mustard or mustard gas is a chemical weapon that causes blisters on the skin and in the lungs. Its chemical formula is C₄H₈Cl₂S. What is the molar mass of this compound?

Answer 1

M = (4 x 12.01g/mol) + (8 x 1.008g/mol) + (2 x 35.45g/mol) + (1 x 32.07g/mol) = 159.074g/mol

Question 2

The smallest particle of an element that retains the chemical properties of that element.

Answer 2

Atom

Question 2

A model of the atom that assumed the electrons were negatively charged particles spread throughout a diffuse, positively charged matrix.

Answer 2

The Plum Pudding Model

Question 2

The short range proton-neutron, proton-proton, and neutron-neutron forces that hold the nuclear particles together

Answer 2

Nuclear Forces (or the Strong Force)

Question 2

Strontium nitrate is used as a red colorant in fireworks. The formula for the compound is Sr(NO₃)₂. What is the formula mass of this compound?

Answer 2

M = (1 x 87.62u) + (2 x 14.01u) + (6 x 16.00u) = 211.64u

Question 2

How many formula units are there in 0.084mol of potassium sulfide, K₂S?

Answer 2

Question 2

How did Rutherford explain the mass and volume of the nucleus?

Answer 2

The nucleus occupies only a tiny volume of the entire atom, yet contains over 99.9% of the atom’s mass. Therefore it is a very dense, positively charged area.

Question 3

The tiny central core of an atom having a dense, positive charge

Answer 3

Nucleus

Question 5

A symbol that indicates the identity of a particular atom using its symbol, along with the number of protons as a subscript and the mass number as a superscript, preceding the symbol.

Answer 5

Nuclide symbol

Question 5

A mass defined as being exactly 1/12th the mass of a carbon-12 atom.

Answer 5

Atomic mass unit (u or amu)

Question 6

The identity of an atom is determined by the number of these in the atom.

Answer 6

Protons

Question 7

The total number of protons and neutrons in a nucleus

Answer 7

The mass number (A)

Question 8

What is the mass of 0.085mol of iodoform (CHI₃), a chemical used as a disinfectant, whose smell is sometimes described as the smell of a hospital?

Answer 8

Question 9

A neutral subatomic particle, found in the nucleus of an atom.

Answer 9

Neutron

Question 10

The general term for a specific isotope of an element

Answer 10

Nuclide

Question 12

Calculate the number of moles of lithium sulfate in a 16.5g sample of the compound.

Answer 12

Question 14

A law that states that “a chemical compound contains the same elements in exactly the same proportions by mass regardless of the size of the sample or source of the compound.”

Answer 14

The Law of Definite Proportions

Question 15

How many moles are there in a 2.61g sample of aluminum carbonate, Al₂(CO₃)₃?

Answer 15

Question 16

The relative charges of the electron, neutron, and proton, in that order.

Answer 16

-1, 0, +1

Question 17

J.J. Thomson’s cathode ray tube experiment led to the discovery of which subatomic particle?

Answer 17

The electron

Question 18

If a sample of thiourea (CH₄N₂S) contains 2.91 x 10¹⁸ molecules, how many moles is this equal to?

Answer 18

Question 19

What is the mass of 6.90mol of Iridium?

Answer 19

Question 20

In the hyphen notation carbon-12, the 12 represents this.

Answer 20

The mass number

Question 21

The center of an atom, composed of protons and neutrons.

Answer 21

Nucleus

Question 22

The atom that was chosen as the standard for the relative atomc mass scale.

Answer 22

Carbon-12

Question 22

What parts of Dalton's atomic theory are now known to be incorrect?

Answer 22

1. Atoms are not indivisible (they are composed of smaller particles). 2. All atoms of a given element are not necessarily identical (many elements have isotopes).

Question 23

How many hydrogen atoms are there in 4.50mol of diammonium phosphate, (NH₄)₂HPO₄?

Answer 23

Question 25

A law that states "mass is neither created nor destroyed during ordinary chemical reactions or physical changes."

Answer 25

The Law of Conservation of Mass

Question 26

If a sample of silver contains 5.97 x 10²⁴ atoms, how many moles are there?

Answer 26

Question 28

Selenium has five different stable isotopes. Using the data below, calculate that average atomic mass of selenium to two decimal places. Nuclide Isotopic Mass %Abundance Se-74 73.922amu 0.89% Se-76 75.919amu 9.37% Se-77 76.920amu 7.63% Se-78 77.917amu 23.77% Se-80 79.917amu 49.61% Se-82 81.912amu 8.73% Note: You may have to stop in the middle of the calculation, press equals, and then continue.

Answer 28

(73.922u x 0.0089) + (75.919u x 0.0937) + (76.920u x 0.0763) + (77.917u x 0.2377) + (79.917u x 0.4961) + (81.912u x 0.0873) = 78.96u

Question 29

The number of protons in the nucleus of an atom is given by this number.

Answer 29

The atomic number (Z).

Question 31

This negatively charged, smallest subatomic particle is about 1,836 times lighter than the other two subatomic particles.

Answer 31

Electron

Question 32

How many molecules of carbon monoxide would there be in 3.8mmol?

Answer 32

Question 34

Complete the table:

Answer 34

Question 35

What did Robert A. Millikan's oil drop experiment allow scientists to determine?

Answer 35

The mass of the electron

Question 36

How many oxygen atoms in NaNO3? How many in Ca(NO₃)₂ ? How many in Al(NO₃)₃? What is the general rule for counting atoms in parentheses?

Answer 36

3, 6, 9; multiply the subscript outside the parentheses by the subscripts inside the parentheses.

Question 37

Ernest Rutherford's gold foil experiment gave experimental evidence suggesting that atoms have these.

Answer 37

Nuclei

Question 38

A law that states "if two or more different compounds are composed of the same two elements, then the ratio of the masses of of the second element combined with a certain mass of the first element is always a ratio of small whole numbers."

Answer 38

The Law of Multiple Proportions

Question 39

A positively charged subatomic particle, found in the nucleus of an atom.

Answer 39

Proton

Question 40

Atoms of the same element having a different number of neutrons.

Answer 40

Isotopes

Question 41

The weighted mass of all the naturally occurring isotopes of an element.

Answer 41

Average atomic mass