Chemistry Unit 2 Summative Review - Atomic Structure & Molar Qua

​Chemistry

Unit 2 Summative review​

History of Atomic Theory & Atomic Structure

• History of Atomic Theory 2 questions x 5 pt = 10 pts

• Atomic Structure 10 questions x 2 pt = 20 pts

• Molar Mass 10 questions x 2 pt = 20 pts

• Moles to Mass 5 questions x 2 pt = 10 pts

• atoms to moles 5 questions x 2 pt = 10 pts

• Multi - Step Conversion. 2 questions x 2 pt = 4 pts

• Essay Question - Conversion. 2 questions x 3 pt = 6 pts

• % Composition (Essay) 1 question x 5 pt = 5 pts

• Empirical Formula (Essay). 1 question x 5 pt = 5 pts

• Molecular Formula (Essay) 1 questio x 5 pt = 5 pts

• Calculate Atomic Mass (Essay) 1 question x 5pt = 5 pts

​Democritus 460 b.c.

​Atomos - "Uncuttable"

​

​

Multiple Choice

Used the word "atomos" to decsribe the uncuttable (indivisible) atom.

• Democritus

• Thomson

• Bohr

• Dalton

Multiple Choice

Which of the following is/are conclusions based on Rutherford’s gold foil experiment?

• Atom is mostly empty space

• The nucleus is positively charged

• The atom has a small dense nucleus

• All answers are correct

Multiple Choice

He discovered electrons

• J.J. Thomson

• John Dalton

• Ernest Rutherford

• Niels Bohr

• The dense central core of an atom

  • Contains both protons and neutrons

  • Neutrons stop protons from repelling each other

• Contains most of the mass of the atom​

  • Mass is the sum of protons and neutrons​

​

​The Nucleus

Multiple Choice

Ions are: 

• atoms with a positive or negative charge
• atoms with no charge
• atoms with ONLY a positive charge
• atoms with ONLY a negative charge

Multiple Choice

An atom becomes _______ when it loses electrons.

• Positive
• Negative
• Neutral
• Invinsible

Multiple Choice

An atom becomes _________ when it gains electrons.

• Positive
• Negative
• Neutral
• Invinsible

Multiple Choice

What is the charge of an atom with 5 protons, 5 neutrons, and 7 electrons?

• 0

• +5

• +2

• -2

• We distinguish between different elements based on their atomic number

  • The number of protons they have

• The Mass number is the number of neutrons + number of protons in an atom

  • Mass No. is measured in atomic mass units (amu)​

​

​Atomic number and mass number

Multiple Choice

If an element contains 13 protons and 12 electrons what would be its overall charge?

• +1

• -1

• +13

• -13

Multiple Choice

A Bromine ion gains 1 electron, which of the following is the correct symbol for a Bromine ion?

• Br^-1

• Br⁺¹

• Br⁺⁷

• Br^-7

Multiple Choice

How would you write a Sulfur that has gained 2 electrons?

• S⁺²

• S^-2

• S⁺⁶

• S^-6

Multiple Choice

If an atom of Boron has 5 protons how many electrons will it need to have to be neutral?

• 3

• 4

• 5

• 6

Multiple Choice

The molar mass of an element is numerically equal to the

• element’s atomic mass.

• number of neutrons found in the element.

• element’s atomic number.

• mass of one atom of the element.

Fill in the Blank

How many protons are in a Carbon atom?

(Type a whole number only!)

Multiple Choice

What is the charge of a neutron, and what is its location in an atom?

• Neutral charge, located in nucleus.

• Negative charge, located in nucleus.

• Neutral charge, located in the orbitals/cloud.

• Negative charge, located in the orbitals/cloud.

Multiple Choice

What is the charge of a proton, and what is its location in an atom?

• Neutral charge, located in nucleus.

• Positive charge, located in nucleus.

• Neutral charge, located in the orbitals/cloud.

• Positive charge, located in the orbitals/cloud.

Multiple Choice

What is the charge of an electron, and what is its location in an atom?

• Negative charge, located in nucleus.

• Neutral charge, located in nucleus.

• Negative charge, located in the orbitals/cloud.

• Neutral charge, located in the orbitals/cloud.

Multiple Choice

An electron and proton are ALIKE because...

• Neither has a charge.

• Both are charged.

• Both are in the nucleus.

Multiple Choice

A neutron and proton are ALIKE because...

• Neither has a charge.

• Both are charged.

• Both are in the nucleus.

Multiple Choice

Protons are DIFFERENT from neutrons because...

• One is in the nucleus, the other is in the orbitals/cloud.

• One has a charge, the other does not.

• Both are in the nucleus.

​Now Isotopes!

​All carbon atoms have 6 protons in the nucleus, but there may be 6, 7, or 8 neutrons. These are called isotopes of carbon. There are isotopes of every element!

Isotopes, mass number

An atom's mass is its total of protons and neutrons . The electron cloud mass is small enough to ignore.

Carbon-12, carbon-13, & carbon-14 are carbon's isotopes. 12, 13, and 14 are their masses.

Multiple Choice

The mass number of an atom is the number of ...

• Electrons plus Protons

• Neutrons plus Electrons

• Protons plus Neutrons

Multiple Choice

What Greek philosopher was the first person to propose the idea that matter is made of tiny particles called atoms

• Democritus

• Dalton

• Thompson

• Rutherford

• Bohr

Fill in the Blank

In an atom of boron-11, has a mass number of 11 how many neutrons are present?

Type a whole number!

(Use your periodic table!)

Multiple Choice

Which subatomic particle identifies an element?

• Protons

• Neutrons

• Electrons

• Protons and Neutrons

Multiple Select

Which particles have a charge (check all that apply)?

• Protons

• Neutrons

• Electrons

Multiple Select

Which particles are found in the nucleus?

• Protons

• Neutrons

• Electrons

Multiple Select

Which particles account for almost all the mass of an atom?

• Protons

• Neutrons

• Electrons

Multiple Choice

Magnesium's atomic number is 12. This means that a magnesium atom has

• 12 protons in its nucleus

• A total of 12 protons and electrons

• 12 neutrons in its nucleus

• A total of 12 neutrons and electrons

Multiple Choice

A potassium atom has an atomic mass of 39. Its atomic number is 19. How many neutrons does the iron atom have?

• 19

• 39

• 20

• 58

Multiple Choice

Two atoms that are different isotopes of the same element have

• a different number of protons but the same number of neutrons

• the same number of protons and the same number of neutrons

• a different number of protons and a different number of neutrons

• the same number of protons but different numbers of neutrons

Isotope Abundance and Atomic Mass

• In nature, most elements occur as a combination of two or more isotopes

  • Each isotope has a natural percent abundance​

• The average atomic mass is the weighted average of the masses of its isotopes

  • a weighted average reflects the relative abundance of each isotope found in nature

• Calculated Atomic Mass: The more common an isotope is, the more important it is in atomic mass calculations

  • Step 1: ​multiply the mass of each isotope by its natural abundance

  • Step 2: add the products of all the weighted isotopes masses

Chem 1 | Unit 1 Lessons 2 & 3

Atomic Mass Estimations Practice Problem 2

• Consider a hypothetical element, X, that has three isotopes. Calculate the weighted- average atomic mass of the element from the following data:

  • ​Step 1: Multiply each atomic mass by it's abundance

    • 85.32 x 0.10

    • 87.51 x 0.70

    • 88.10 x 0.20

  • Add the sum of the relative masses together

Chem 1 | Unit 1 Lessons 2 & 3

​Isotope	​Abundance	​Atomic Mass
​X-85	​10%	​85.32 amu
​X-87	​70%	​87.51 amu
​X-88	​20%	​88.10 amu

Multiple Choice

How is average atomic mass determined?

• By adding all of the protons and neutrons together.

• by summing the masses of the element's isotopes, each multiplied by its natural abundance on Earth

• By multiplying of often protons and neutrons occur and adding up the averages.

Fill in the Blank

Element X has two naturally occurring isotopes. One isotope has a mass of 10 amu with a relative abundance of 20%. The other isotope hasa mass of 11 amu and relative abundance of 80%. What is the average atomic mass of Element X

.

Multiple Choice

4.35% of all X atoms have a mass of 39.946 amu. 83.79% have a mass of 41.941 amu, 9.50% have a mass of 42.941 amu, and 2.36% have a mass of 43.939 amu. What is the average atomic mass of atom X?

• 41.97 amu
• 42.19 amu
• 10.43 amu
• 40.04 amu

Multiple Choice

If an atom has 5 protons and 6 neutrons what is the proper name of the isotope?

• Boron-1

• Boron-11

• Carbon-11

• Carbon 11

• Boron Carbonate

Molar Conversions

By Mihir Paranjape

Molar Mass

Some text here about the topic of discussion

If atoms are inside parenthesis, simply multiply the number inside by number outside. e.g.

(CH₃COOH)_3​

​Element	​number inside	​Number out	​Total
​C	​1	​3	​1x3 = 3
​H	​3+1=4	3​	​4x3 = 12
​O	​1+1=2	3​	​2x3 = 6

Multiple Choice

The unit g/mol is the unit of

• atomic mass.

• atomic number.

• molar mass.

• atomic mass number.

​1 mole of CO has a mass of 28 g/mole

​

What is the mass of 4.25 moles of CO?​

​4.25 moles CO

​1 mole CO

​28 g

​= 119 grams

​1 mole of any element contains 6.02 x 10²³ atoms

​

How many atoms are in 1.25 moles of carbon?​

​

​1.25 moles C

​1 mole carbon

​6.02 x 10²³ atoms

​= 7.52 x 10²³ atoms

Multiple Choice

How many moles are in 2.408 x 10²⁴ molecules of O₂?

• 2.408

• 4

• 0.25

• 1

Fill in the Blank

How many moles are in 91 g of CO₂

Round up two places after decimal

Atomic Mass

C = 12

O = 16

.

Multiple Choice

Using a periodic table, determine which of the following quantities is not equal to 1.00 mole.

• 6.02 x 10^23 carbon atoms

• 79.9 g Br

• 26.0 g Fe

• 65.4 g Zn

Multiple Choice

The number 6.02 x 10²³, which is the number of particles found in a mole is called ....

• molar mass
• mole
• Avogadro's number
• hydrate

Multiple Choice

What is the molar mass of Hydrogen Peroxide (H₂O₂)?

• 48 g/mole

• 34.0 g/mole

• 36.5 g/mole

• 35.5 g/mole

Multiple Choice

Which is the correct molar mass for the compound FeSO₄

• 103.9

• 152.0

• 415.4

• 247.9

Multiple Choice

Which of the following  setups will correctly convert 2.50 moles of sodium to grams of sodium?

• A
• B
• C
• D

Multiple Choice

How many moles are in 16.94g of water?

• 16.94 mol H₂O

• 0.9411 mol H₂O

• 305.3 mol H₂O

• 1.063 mol H₂O

Multiple Choice

What is the number of moles of Beryllium in 36 g Be?

• .25 mol
• 45.0 mol
• 340 mol
• 4.0 mol

Multiple Choice

How many hydrogen atoms are in the compound: (NH₄)₂CO₃

• 3
• 4
• 6
• 8

Multiple Choice

How many moles are contained in 45 grams of aluminum?

• 27 mol
• 1215 mol
• 1.7 mol
• 57 mol

Multiple Choice

How many molecules are in 64 g of O₂?

• 2

• 1.204 x 10²⁴

• 3.01 x 10²³

• 6.02 x 10²³

• ​Lets work some other problems on the board:
  
  % Composition

  Calculate Empirical Formulas

  Calculate Molecular Formulas

Percent Composition Formula

Perhaps a simpler formula is this. (From back page of your Reference Tables)

"Mass of part" is the mass contribution from the specific element of interest. (but can also be a polyatomic ion or H₂O)

"Mass of whole" is the total mass of the formula (a.k.a... gram formula mass)

Multiple Choice

Considering the generic formula for percent composition below, what number would go in the numerator if you were attempting to solve for the percent composition of Hydrogen in $$CH_4$$  ?

$$\%\ comp\ =\frac{Mass\ contribution\ from\ the\ specific\ element}{Total\ mass\ in\ formula}\ x\ 100$$  

• 16.05 grams

• 4.04 grams

• 12.01 grams

• 48.04 grams

​Sometimes, the empirical formula is also the molecular formula ( ex. H₂O)

Multiple Choice

What is the empirical formula for C₄H₆?

• CH

• CH₃

• C₂H₃

• C₄H₆

Multiple Choice

Which pair has the same empirical formula?

• NaCrO₄ and Na₂Cr₂O₇

• C₂H₄O₂ and C₆H₁₂O₆

• C₃H₆O₃ and C₂H₆O₂

• CH₄ and C₂H₆

​How to calculate empirical formula from percent composition

In order to calculate the empirical formula of a compound we must first determine the relative masses of elements present- 

• The relative masses will give us what?

  •  the ratios of the elements present in the compound. 

• The ratios will give us what?

  •  the subscripts

• One way to find the relative masses in the compound is to measure the masses that react to form the compound

• Write this down: Percent to grams, grams to moles, divide by smallest, multiply til whole

​Percent to grams, grams to moles, divide by smallest, multiply til whole

​Try this one.....