Chemistry module 2 - DETAILED

what is the relative charge of protons?

1

what is the relative charge of neutrons?

0

what is the relative charge of electrons?

-1

what is the relative mass of a proton and a neuton?

1

what is the relative mass of an electron?

• 1/1836

what is the location of protons and neutrons?

• nucleus

what is the location of an electron?

orbitals

what is an isotope?

• atoms of the same element with different numbers of neutrons = different masses

what is the mass number?

• total number is protons and neutrons in the nuecleus

what is atomic number?

• total number of protons in a nucleus

what is the element symbol?

• atoms have the same number of protons and electrons because they are neutral

what ion do noble gases form?

• do not form ions they are inert

what ion do transistion metals form?

• they form a range of different positive charge ions

how can the charge of an ion be shown?

• roman numerals in the number of the ion

what is a polyatomic ion?

• contains more than 1 atom

what is the formula of the ammonium ion?

NH4+

what is the formula of the hydroxide ion?

OH-

what is the formula of the nitrate ion?

NO3 -

what is the formula of a nitrite ion?

NO2 -

What is the formula of a hydrogencarbonate ion?

HCO3 -

what is the formula of a manganate(VII) ion?

MnO4 -

what is the formula of a carbonate ion?

CO3 2-

what is the formula of a sulfate ion?

SO4 2-

what is the formula of a sulfite ion?

SO3 2-

what is the formula of a Dichormate(VI) ion?

Cr2O7 2-

what is the formula of a phosphate ion?

PO4 3-

what is a cation?

• a postively charged ion

what is a anion?

A negatively charged ion

what does ionic equation show?

• species involved in a chemical reaction

how do we show soluble ionic compounds and strong acids?

• are shown as constituent ions (indicated using the Aq state symbol)

what is a constituent ion?

-An ion that is present in an ionic compound.

how do we show insoluble ionic compounds and covalent compounds?

• indicated by the state symbols (s) (l) (g)

what are spectator ions?

• ions which do not change in a chemical reaction

what do we do to aqueous compounds when writing an ionic compound?

• separate into ions

what do we do to insoluble ionic compounds and covalent compounds when writing an ionic compound?

• leave the compound alone and do not separate the ions

explain how to write a ionic equation?

• first separate the aqueous compounds into ions
• then cancel out the same ions from both sides from the aqueous compounds
• make sure to write the state symbols for all of the ions and compounds

when do we use relative formula mass?

• used of simple covalent

when do we use relative molecular mass?

• only used for simple covalent molecule

what is the relative formula mass?

the sum of the relative atomic masses of the atoms in a molecule

what is the relative atomic mass?

The weighted mean mass of an atom relative element compared to one twelfth of the mass of an atom of carbon 12.

what is the composition by mass formula?

(Total mass contribution by atom/total mr of compound) x 100

what is relative isotopic mass?

• is the mass of an isotope relative/compared to 1/12 of the mass of an atom of carbon-12

what is the mass of the carbon-12 isotope?

• excatly 12 atomic mass units (12u)
• 1/12 of the mass of an atom of carbon is is 1 atomic mass unit (1 u)

how are the abundancy of isotopes determined?

• mass spectrometry

can you explain mass spectrometry?

• sample is vaporised and the ionised to form +1 ions

• ions are accelerated through the spectrometer

• heavier ions move slowly and more difficult to deflect than lighter ones(ions are separated)

• ions reach detector and a signal is generated (greater the abundance the larger the signal)

what does the spectrometer measure?

• the mass to charge ratio (m/z) of each ion (since 1+ is the relative isotopic mass)

how do we calculate the relative atomic mass from percentage abundances?

Ar = ((mass x abund)+(mass x abund)/total abundance)

what is oxidation number?

• measure of the number of electrons involved in bonding to a differnt element

• in redox reactions the change in oxidation number for oxised species equals the change in oxidation number of the reduced species

what is the oxidation of pure elements?

0

what is oxidation number of groups 1

2

what is the oxidation of flourine?

always -1

what is oxidation of hydrogen when bonded to a metal?

-1

what is the oxidation of oxygen when it reacts with fluorine?

+2 because fluorine is more electronegative

what is the oxidation number of oxygen in peroxides?

-1

what is the oxidation number of chlorine when it reacts with fluorine or oxygen?

• positive oxidation number

how do we calculate oxidation number?

• assign known oxidation numbers from rules
• overall charge(sum of the oxidation numbers)
• calculate oxidation number for the unknown atom

how can we use roman numerals in systematic naming?

• roman numerals are used to indicate the oxidation number of an element that can exist in more than one oxidation state

what is a redox reaction?

what is redox reaction in terms of electrons and oxidation number?

• chemical reaction which involves both reduction and oxidation processes- gain of electrons- the decrease of oxidation number

what is oxidation in terms of electrons and oxidation number?

• increase of oxidation number- loss of electrons

what is disproportionation reaction?

• in the some redox reactions the same substance is both oxidised and reduced

what is a oxidising agent?

• cause oxidisation of another species

• cause the other species to lose electrons

• oxidation agents are electron acceptors

• oxidising agent get reduced in the process

what is reducing agents?

• cause reduction of other species- cause the other species to gain electrons- reducing agents are electron donors- reducing agents get oxidised in the process

what are subshells made out of?

• orbitals

what is a orbital?

• is a region of space around the nucleus of an atom which can hold up to 2 electrons with opposite spin

what are the characteristics of s orbitals?

• can hold up to 2 electrons- have spherical shape- each shell contains 1 s- sub shell- s sub shells are made from 1 s orbital- can hold 2 electrons

What are the characteristics of p orbitals?

• have dumbell shape- energy levels 2-4 contain 1 p sub shell- p sub shells are made from 3 p orbitals- can hold a maximum of 6 electrons

What are the characteristics of d orbitals?

• can hold a max of 10 electrons- energy levels 3-4 contain 1 d sub shell- a subshells are made up of 5 d orbitals

What are the characteristics of f orbitals?

• can hold a max of 14 electrons- energy level 4 contain 1 f sub-shell- f sub shell are made from seven f orbitals

what is hunds rule?

• electrons occupy orbitals in sub shell singly before pairing up

how do electrons fill subshells?

• occupy the lowest energy sub shell first then the next lowest and within a sub shell the orbitals have the same energy

what is the equation which links abundance and relative atomic mass of two isotopes?

percentage abundance = (pull/difference)x100

what is one mole?

• is the amount of substance that contains the same number of particles as there are atoms in 12g of carbon 12

what is Avogadro constant?

6.02x10²³

what is the equation which links mass and number of moles?

mass = number of moles x Mr

what equation links avogadro constant and number of moles?

number of particles = number of moles x 6.02x10²³

what is empirical formula?

• is the simplest whole number ratio of each type of atom in a compound

what is molecular formula?

The molecular formula gives the actual numbers of atoms of each element in a compound

how d we calculate empirical formula?

• divide mass/mr to get number moles

• then divide all the moles by the smallest number of moles to get the simplest ratio

• multiply to get whole number

whats the difference between percentage composition and mass in grams when calculating empirical formula?

• there is no difference you still will follow the same process

how do we calculate the molecular formula from the empirical formula when your given the mr?

• divide mass/mr to get number of moles

• then divide moles by the smallest mole to get the simplest ratio

• now calculate the mr of the empirical formula

• divide mr of molecular formula / mr of empirical formula to get molar ratio

• now multiply the empirical formula with the ratio to get molecular formula

what is the amount of substance equation which links moles and mr?

mass = moles x Mr

what is limiting reagent?

• limits the maximum/theoretical amount of product that can form
• reactant used up in the reaction

what is excess reagent?

the reactant that is not completely used up in a reaction

how do we determine if a reactant is excess or limited?

• calculate the number of moles and compare the moler ratio

• highest number of moles for reactant is excess and lower one is limited

• calculate the mass of the product produced using the moles of the limited reactant

what do we do when the molar ratio of the limited and the excess if not 1:1?

• if the limited reagent to the excess is 2:1 we divide the limited by 2 and use that number of moles

• eg limited = 0.05

• excess = 0.1 we would us the 0.05 as the moles

• 0.05/2 = 0.025 moles is what we will use

why is the yield of chemical reactions never 100%?

• side reaction may occur
• reaction may not go to completion
• reaction may be reversible
• product may be lost during extraction process

what is the equation for percentage yield?

percentage yield = (actual amount/ maximum theoretical amount) x 100

what is atom economy?

• is a measure of efficiency of a reaction in terms of atoms involved and can be calculated from balanced equation

what does atom economy not consider?

• doesnt deal with the efficiency of the reaction as a process (reaction not going to completion

how can we calculate atom economy?

(molecular mass of desired product/sum of molecular masses of all products) x 100

when carbon dioxide is prodcued why does the atom economy decrease?

• relatively high molecular mass of CO2 is produced

what is teh atom economy of an addition reaction?

• the atom economy is 100%

what is teh atom economy of a substitution reaction?

• vbmn

what is the atom economy of elimination reactions?

• the atom economy is less than 100%

why are low atom economies bad for the environment?

• energy used by process has been wasted on by products

• wasted fossil fuels and green house emissions

• by products often have to be treated before disposal

• this extra processing requires energy and resources (other chemicals)

how can we resolve low atom economies of a reaction?

• recycle or find use for the waste products

what is the molar gas volume at room temperature?

• 24dm^3
• one mole of any gas at RTP occupies a volume of 24dm^3

what is the equation which links moles and molar gas volume at room temperature?

volume of gas (dm^3) = moles x 24

how do we convert cm^3 to dm^3?

divide by 1000