Chem mid term test

Matter definition

everything that takes up space and has mass is made of matter

• some of it is more easily visible (water, trees)

• some is not immediately visible (air)

Atoms structure and definition

Subatomic particles that are the building blocks for everything and can be found independently or they bond to create molecules

• positively charged nuclei with protons and neutrons

• Outer cloud area contains negatively charged electrons

• no. of electron = protons so no net charge

What do the states of matter depend on

solid liquid, and gas depend on pressure and temperature

• Any change of state is a physical change

Features of a solid

Atoms are packed together and vibrate at a fixed point

• particle don’t move relative to each other

• Fixed shape and volume

Features of a liquid

Atoms/molecules are attached but able to move freely over and around each other

• fixed volume

• Assumes shape and container

features of a gas

Atoms separated by large distances

• barely interact with one another

• expands to fill container

what are the specialised names for different element groups

• Group 1 = alkaline metals

• Group 2 = Alkaline earth metals

• Group 3-12 = transition metals

• group 17 = halogens

• Group 18 = noble gasses

• Top of separated layer = Lanthanides

• Bottom of separated layer = actinides

what are element grouped based on

grouped based on electron configuration and similar chemical properties

• also group in a certain table on State of matter (liquid= Metalloids, Solid = metals and gasses = Non-metals)

what is an ion and what are the two types

an atom with the tendency to gain or lose an electron in order to achieve a full octet

• cations: positively charged (lost electron)

• Anions: negatively charged (gained electron)

how does ionic bonding occur

Through the bonding of a non-metal anion and a metal cation that allow the other to gain a full octet

• anions and cations are attracted to one another due to difference in electronegativity

what groups are more likely to form cations and anions

Groups 1,2 and 13 form cations with a +1, +2 and +3 charge, respectively

Groups 17, 16 and 15 form anions with a charge of -1, -2 and -3, respectively

Transition metal are able to form either depending of the atom they bond with

Isotopes

Atoms that have a different number of neutrons to protons, often due to radioactive decay

• leads to a different mass number

Isotope dating + isotopes analysed

a techniqure used to dtermine the age of an object based on the radioactive decay of ceratin element present in said object

¹⁴C (animal and plant matter <50,000 y.o)

⁴⁰K (rocks >100,000 y.o)

¹⁷O or ¹⁸O (ice core dating)

why do we use roman numerals in Nomenclature

Used for ionically bonded molecules, one of which is a transition metal that doesn’t strictly for a cation or an anion

• The numeral indicate the charge of the Metal in the molecule

• Charge of the metal will balance out the charge of the other ion

when are suffixes like Di and tri not used

• in ionic bonding

• when polyatomic ions are used

pure substance

a substance that can not be separated by any physical process

• can be an element or a compound

Mixture ( examples)

a substance composed of two or more substances that have been physically combined

• each component retain original properties

• can be separated by physical means

what is an element vs and compound

Element: can be broken down into simpler substances

Compound: made up of multiple elements

homogenous vs heterogenous mixtures

Homogeneous: particles that are mixed but can’t be distinguished or easily physically separated

Heterogeneous: are able to distinguish particle and can be easily separated

what is a mole

A measurement used to count the number of atoms or molecules

• 1 mole = 6.02 × 10²³ atoms/molecules

• 6.02 × 10²³ = avogardro;s number and comes from the number of carbon atoms found in 12g of carbon

relationship between moles and atomic mass

the mass of 1 mole = average atomic mass or Molar mass of that element in grams

formula for number of moles and it rearranging

No. of moles = mass (g)/Molar mass (g/mol)

n=m/M

m= n x M

M=m/n

what is a chemical reaction and when does it occur

occurs when chemical bonds are formed due to

• atoms combining

• molecules combining

• Molecule or compounds decomposing

• atoms exchanging molecules

struture of a chemical equation

A + B —→ C + D

what does it mean to balance a chemical equation

making sure the same number of atoms of each element can be found on either side of the equation

what is Stoichiometric coefficenit

The big number placed before an element indicates how many there are

• no. of molecules

what are the steps to balancing a chemical equation

1. write out an unbalanced equation in chemical formula (N + O = NO₄)

2. Adjust coefficients so the same number of each element appears on both sides of the equation ( write a table to summarise how many of each element appear on either side)

a) balance elements other than O and H first

b) Balance polyatomic ion groups that appear on both sides

c) balance products of alone element like O₂

what is density (measurments)

the amount of a substance in a particular volume

• d = mass(g) / volume (ml)

• units = g/ml or gcm^-3

what is a polyatomic ion

Multiple atoms combined together with one often being an oxygen

• have a net + or - charge rather than being neutral

what are the polyatomic anions + charge

charge of -2

• SO₄ or SO₃

• Cr₂O₇ - dichromate

• CO₃

charge of -3

• PO₄

charge of -1

• NO₃ or NO₂

• ClO - Hypochlorite

• HCO₃ - hydrogen carbonate

• CH₃COO - acetate

• CN

• OH

what are the polyatomic cations + charge

• NH₄⁺

• H₃O⁺

Ionisation in water

Substance reacts with water to produce an ion

• e.g HCl + H₂O —> H₃O⁺ + Cl^-

Dissociation in water

Substance dissassociate in water to form two ions

• NaCl + water —> Na⁺ + Cl^-

nuetralisation

An acid and a Base react to produce water and a salt (whatever is left that isn’t water)

Precipitation

When a solid forms from ions in an aqueous solution

what do A and Z represent

A= atomic number (number of protons)

Z = atomic mass ( Protons + neutrons)

how to name basic ionic compounds

Place the cation(metal) before the anion (non-metal)

• the number of moles of ecah element need to balance out the charges between the two elements

• should be written at lowest integer value ( 2a + 4b no, a + 2b = yes)

when is the suffix ide used

used for binary compounds with two of the same element or different elements

binary = 2 molecules

when are the suffix ate and ite used

-ite is used for - charge ions that have less oxygen atoms than their positive counterpart

• Hypo- -ite = 1-2 O

• ite = 2-3 O

• ate = 3-4 O

• Per- -ite = 4+

when are the sufixes ic and ous used

if the polyatmoic ion or conjugated base ends in ate = used -ic acid

if it ends in -ite use -ous acid

used of suffixes and polyatomic ions with differing oxygens

SO₄ = ate

SO₃ =ite

CO₃ = ate

NO₃ = ate

NO₂ = ite

PO₄ = ate

ClO₄ = per ate

ClO₃ = ate

ClO₂ = ite

ClO = hypo ite

what is a limiting reactant

The factors that limits the number of molecules of a product that can be made in a recation

• if you need 2 N and 4O to make NO₂ but you only have 1N then you can only make 1 NO₂

• O is in excess

what is a stoichemtric ratio

A ratio of how many reactants and needed to create a certain amount of products

what is a solution

Homogenous mixture of two or more substance

• solvent = what solue is dissovelde in (often water)

• solute = what dissolves in water

what is an aqeous solution

a solution where the solvent is water

• solute can be in any state of matter

what is a concentraion + formula

the quality of a substance dissolved in a quantity of solution

c= amount of solute(moles)/ Volume of solvent (L)

c= n/v

v= n/c

n=cx v

what is the dilution formula

Concentration1 x Volume 1 = Concentration 2 x volume 2

v1 = c2 x v2 /c1

what is a colloid

a solution where particles are large enough to be seen (reflect light) but too small to settle

• e.g emulsions like milk or mayo

what is a suspension

a solution where particles are large enough to be seen and can settle to the bottom

• heterogenous mixtures

what is a standard solution

A solution at which the solute has reached its maximum concentration in a given amount of solute

• reported as max amount that dissolves in 100g of water

how to calculate mass percentage

no. of atoms(stoichiometric) x atomic mass of atoms/ molecule mass x 100