Intro to Chemistry & Moles/Mass

Question 1

What is Chemistry?

Answer 1

The study of matter.

Question 2

What is the equation for moles?

Answer 2

Moles = Mass (g) / Molar Mass

Question 3

What is Avogadro’s Number?

Answer 3

6.02*10^23

Question 4

What is a Mole?

Answer 4

One mole is the Avogadro’s number of particles in a substance.

Question 5

What are the types of chemical reactions?

Answer 5

Combination
Decomposition 
Single displacement/replacement
Double displacement/replacement
Combustion

Question 6

What is Combination?

Answer 6

Two or more elements combined to make one compound.

A + B - AB

Question 7

What is decomposition?

Answer 7

The opposite of combination where one compound breaks down into elements or separate compounds.
AB - A + B

Question 8

What is single replacement?

Answer 8

One element replaces another one in a compound.

A + BC - B +AC

Question 9

What is double replacement

Answer 9

Two elements in two compounds switch places.

AB + CD = AD + BC

Question 10

What is combustion?

Answer 10

Oxygen combines with a compound to give carbon dioxide and water. This is an exothermic reaction, meaning heat is given off.
AB + O2 = CO2 + H20

Question 11

What are the indicators of a reaction?

Answer 11

Emission of light or heat,
Formation of a gas,
Formation of a precipitate,
Change in colour
Emission of odour

Question 12

How do you calculate moles from mass (g)

Answer 12

Mass/Molar Mass

Question 13

How many moles in 58.8g NaCl?

Answer 13

Moles = Mass / Molar Mass

Molar mass for Na = 23
Molar mass for Cl = 35.5
Molar Mass for NaCl = 23 + 35.5 = 88.5g/mol
58.8g (Mass) / 88.5 (molar mass) = 1 Mole

Question 14

How many moles in 4g NaOH?

Answer 14

Moles = Mass / Molar Mass
Molar Mass of NaOH = 40g/mol (23 + 16 + 1)
4g/40 = 0.1 mole

Question 15

How many grams in 1.5 mole CO2?

Answer 15

Moles = Mass / Molar Mass
Mass = Moles * Molar mass
Molar mass of CO2 = 44g/mol (12 + 162)
1.544 = 66g

Question 16

What is Daltons Atomic Theory?

Answer 16

. All matter is made of tiny particles called atoms
. A given element has similar atoms and different to atoms from different elements
. Two or more elements combine to make a compound. A particular compound always has the same kind of atoms and always has the same number of each kind of atom
. A chemical reaction involves the rearrangement, separation or combination of atoms. Atoms are never created nor destroyed.

Question 17

What is the atomic weight (mass)?

Answer 17

Number of protons + number of electrons

Question 18

What is an isotope?

Answer 18

An element with the same number of protons but different numbers of neutrons.

Question 19

What are electron energy levels?

Answer 19

Each electron has a specific energy known as an energy level. All the electrons with the same energy are grouped into the same energy level. Each energy level is assigned with a number (n) beginning with n-1, n=2, up to n=7.

Question 20

What is Quantum Mechanics?

Answer 20

Describes the arrangement of atoms in terms of:

1. main or principle energy levels
2. energy subshells
3. Orbitals (space occupied within the atom)

Question 21

What is the principle energy level?

Answer 21

Contains elements that are:

1. Close in energy
2. Similar distances to the nucleus
3. Have values of 1,2,3,4,5,6….
4. Maximum number of electrons are 2n^2

Question 22

What are energy levels (shells)?

Answer 22

A group of electrons with the same principle quantum number (n).
The first shell (n=1) has the lowest energy level then shell 2 and so on.
The maximum number of electrons per shell is 2n^2.

Question 23

What are energy subshells?

Answer 23

Sub energy levels within energy levels. All the electrons in the subshell have the same energy. Designated s,p,d,f.
Sublevel energy = s<p></p>

Question 24

What is electron configuration?

Answer 24

List of sub shells containing electrons. In order from lowest to highest energy levels. Number of electrons are shown by the superscript.

Question 25

What are quantum numbers?

Answer 25

Quantised values to describe the electrons in an atom. They are 4 quantum numbers represented by letters n, l, Ml, Ms. These are the Principle Quantum Number, Angular Momentum Quantum Number, Magnetic Quantum Number and Spin Quantum Number.

Question 26

The principle quantum number (n).

Answer 26

n represents the main energy of an electron. Allowable values are n = 1, 2, 3, 4,... maximum electrons per energy level = 2*(n^2) Electrons with higher n level have more energy.

Question 27

What is the calculation for moles to particles and particles to moles?

Answer 27

From moles to particles = moles * Avogadro's number (6.02*10^23) From particles to moles = particles / Avogadro's number

Question 28

What is molar mass?

Answer 28

The mass of one mole of a substance. In grams.

Question 29

What is the periodic table

Answer 29

Shows all of the known elements in one table. The periodic table lists the elements in increasing atomic number in rows (periods). Lists the elements with similar chemical properties in groups. These elements have similar properties as they have the same number of outer electrons.

Question 30

Group trends.

Answer 30

As we increase the atomic number or go for up to down, each atom has another energy level so they get bigger. As we go left to right, atoms get smaller and have the same energy level. However there is more nuclear charge. Also the outer electrons are pulled closer.

Question 31

Ionisation?

Answer 31

The amount of energy required to remove one electron. Removing one electron makes a +1 ion. The further down we go a group, the further the electrons are from the nucleus, plus the more electrons an atom has thus low electronegativity (ability to attract a bonding pair)

Question 32

Angular Momentum Quantum Number (l).

Answer 32

Describes the subenergy level the shape of the orbitals within the sublevels. Allowable values for l are from 0 all the way to n-1. For example of n=3, l = 0, 1 & 2 (n=3-1=2). Each of these values represents a sub level. If l = 0 - s orbital 1 - orbital 2 - orbital 3 - orbital

Question 33

Magnetic Quantum Numbers (ml)

Answer 33

Describe the number of orbitals. ml values are between --l and +l including 0. For example if l = 2, ml = -2, -1, 0, +1, +2. So d orbital has 5 orbitals with a total of 10 electrons (5 orbitals with 2 electrons each).

Question 34

Spin Quantum Number (ms)

Answer 34

Describes that 2 electrons in the same orbital have opposite spin values, -0.5 and +0.5. These are shown as the half up and half down arrows in electron config diagrams.