Flashcards in Help Deck (69)
What is a molecule?
A molecule is a group of two or more non-metal atoms joined together by covalent bonds. Examples of molecules include water oxygen methane and carbon dioxide.
What is an element?
Something that contains only one type of atom, each atom must have the same number of protons.
What all the relative masses and relative charges of protons neutrons and electrons?
Relative mass: 1
Relative charge: +1
Relative mass: 1
Relative charge: 0
Location: in the nucleus
Relative mass: 1/2000
Relative charge: -1
Location: around the nucleus
What is the atomic number?
The number of protons in the nucleus of an atom.
What is the periodic table arranged in order of?
Atomic number of the elements.
What is the mass number of an atom?
The number of protons plus the number of electrons.
What are isotopes?
Atoms of the same element with a different number of neutrons.
What is the relative atomic mass and how do you weight it?
The relative atomic mass is the weighted average mass of all the isotopes of an element.
=(isotope mass x isotope abundance)
What is the empirical formula?
The simplest hole number ratio of elements in a molecule.
How do you work out the molecular formula?
You work out the moles by doing the mass/mr then you times the empirical formula by the number of moles to get the actual number.
How do you calculate percentage yield?
Percentage yield = actual amount of product produced/theoretical amount that could be produced
X100 for a percentage.
Why do ions form?
Atoms a stable when they have a full electron shell. Atoms bond together so that they can gain or lose electrons they need to become stable.
Why do metal ions have an overall positive charge and nonmetal ions have an overall negative charge?
Metal ions have lost negative particles to become ions and nonmetal ions have gained negative particles to become Ions.
What is a redox reaction?
When both oxidation and reduction occurs.
What is an atom?
An atom is the smallest particle of an element that can exist. Atoms are made of protons, neutrons, and electrons.
What are oxidation and reduction?
Oxidation is loss
Reduction is gain
What is a covalent bond?
A shared pair or pairs of elections between two atoms.
How can you use dot and cross diagrams to show the formation of ionic compounds by electron transfer?
You draw the two elements with the first and outer shells and draw on the electrons with dots for one and crosses for the other. Then you draw the ions that will form which have squared brackets, charge signs and you give the dots to the other that needs it.
What is ionic bonding and why?
Ionic bonding is a strong electrostatic force of attraction between oppositely charged ions. The ions formed will be stable and the positive and negative ions will attract each other very strongly.
Why do ionic compounds have high melting points?
Because of strong electrostatic forces of attraction between oppositely charged ions. A lot of energy is required to break them.
In what substances does covalent bonding occur?
Non metal atoms that have too few electrons.
Draw a hydrogen covelent bond
Two H particles with one shell and one shared pair of electrons, none on the outside.
Draw chlorine covalent bond.
Two chorine, 3 shells (2,8,7) then one shared pair of electrons with the other.
Draw water covalent bonding.
Oxygen with 2 shells, 2 shared pair of electrons with different hydrogens. 4 not shared pairs in outer shell.
Draw methane covalent bond.
Two on inner shell 4 on outer shell all covelently bonded with 1 hydrogen to make 8. CH4.
Draw ammonia covalent bond.
N with two on inner shell and 5 on outer shell, 3 covalently bonded with H.
Explain covalent bonding in oxygen.
1 shared pair of electron/2 shared pairs of electrons which would make it more stable.
Draw covalent bonding in ethane.
Two Carbon with one shared pair of electrons between each other.
Each carbon with 3 hydrogen atoms.
Do simple molecular structures have low or high boiling/melting points? Why?
Low because they have relatively weak forces between the molecules.
Do giant covalent structures have low or high boiling/melting points? Why?
Hi because they have strong covalent bonds throughout the structure, E.G.diamonds and graphite.
What is a metal?
A giant structure of positive ions surrounded by a sea of delocalized electrons.
How can metals conduct electricity?
They have a sea of delocalised electrons between the layers which are able to move so they can conduct electricity.
Why are metals malleable?
The layers of ions can slide over one another.
Why do ionic compounds only conduct electricity when molten or in a solution?
The particles are free to move and it is movement that enables the electrons to flow in the external circuit.
What is a catalyst? How does it work?
Something that speeds up the reaction without getting used up itself. It does this by lowering the activation energy by providing an alternate route.
What is electrolysis?
The formation of new substances when ionic compounds conduct electricity.
What is an electrolyte?
A molten liquid or aqueous solution.
Do they conduct? Are their oxides acidic or alkaline?
Metals vs non metals
Metals conduct electricity and have alkaline solutions.
Non metals do not conduct electricity (accept graphite) and have acidic solutions.
Why do elements in the same group have similar chemical properties?
They have the same amount of electrons to gain/lose on their outer shells.
What are the noble gases? Why are they unreactive?
A family of inert gases. They are unreactive because they do not need to gain or lose any electrons to become stable.
How does density of noble gases change as you go down the group?
Lithium reaction with water?
Floats and fizzes becoming smaller until it disappears.
Sodium with water?
Melts into a ball, fizzes rapidly and will burn with an orange flame if placed on filter paper.
Potassium with water.
Metal melts and floats. Hydrogen ignites instants and burns with a lilac flame.
How does reactivity change as you go down the alkali metals and why?
The reactivity increases because the opposite forces of attraction between the protons in the nucleus and electrons in the outer shell become further away so it is easier to lose the outer shell electron.
Chlorine room temp
Bromine room temp
Iodine room temp
How does melting point change as you go down the halogens?
How does melting point change as you go down the alkali metals?
How does the reactivity of halogens change as you go down the group?
It decreases (opposite reason as before).
What halogens will displace what?
Chlorine will displace bromine from sodium bromine solution.
Chlorine will displace iodine.
Bromine will displace iodine.
What happens when aqueous chlorine is added to sodium bromine solution?
Cl2 + 2Br = 2Cl- + Br2
Percentages of gases present in air?
Argon 0.9 %
Carbon dioxide 0.04%
What's the reactivity series?
What is a reducing agent and oxidizing agent?
Reducing agent reduces something
Oxidizing agent oxidizes something
When will iron rust?
When it reacts with oxygen and water.
A source of H+ ions.
A source of OH- ions.
How does rate of reaction change with concentration and why?
Higher concentration means more particles on a given volume so higher collision frequency. Then there are more successful collisions.
For a reaction to occur what must happen?
The particles must collide
The energy at which they collide (collision energy) must be greater than activation energy.
How does rate of reaction change with surface area?
Larger surface area means more sites available for reaction. Collision frequency goes up and there's more successful collisions.
How does rate of reaction change with temperature?
As temperature increases particles have more kinetic enemy so they move round more and collision frequency goes up and there are more successful collisions.
What is the Avagadro's number?
6 x 10^23 particles
How would you investigate the effects of changing surface area of a solid, concentrations of solutions, temperate and the use of a catalyst on the rate of a reaction.
Calcium carbonate and hydrochloric acid.
Cotton wool to stop loss of any solution.
Change conc. of acid.
Heat the acid.
Crush the calcium carbonate into powder.
Use a catalyst.
Measure change in mass.