key concepts

Question 1

what is an endothermic reaction

Answer 1

this is a reaction that takes in energy from the surroundings, usually seen by a fall in temp of the surroundings

Question 2

what is an exothermic reaction

Answer 2

this is a reaction that gives out energy to the surroundings, usually seen by an increase in temp of surroundings

Question 3

what is the formula for ammonium

Answer 3

[NH 4] +

Question 4

what is the formula for nitrate

Answer 4

(NO3)-

Question 5

what is the formula for sulfate

Answer 5

(SO4)2-

Question 6

what is the formula of hydroxide

Answer 6

(OH)-

Question 7

what is the formula of carbonate

Answer 7

(CO3)-2

Question 8

how did rutherford prove that the plum pudding model was wrong

Answer 8

they fired positively charged alpha particles at a thin sheet of gold. if the model was right, most of the particles would pass straight through. although they did, a surprising amount was deflected backwards

Question 9

what are the isotopes of an element

Answer 9

they have different amount of neutrons

Question 10

how do you work out isotopic abundances

Answer 10

-multiply their mass by their abundance and add them.
-then divide by the total abundance

Question 11

in what elements does ionic bonding take place

Answer 11

between a metal and a non metal

Question 12

what are some properties of ionic compounds

Answer 12

-high melting and boiling points
-they dont conduct electricity when it is a solid
-they dissolve easily in water

Question 13

in what elements does covalent bonding take place

Answer 13

between two non metals

Question 14

what are some properties of covalent compounds

Answer 14

-weak forces of attraction
-low melting and boiling points
-dont conduct electricity

Question 15

what are some properties of diamond

Answer 15

-each carbon atom forms 4 bonds
-it is really hard
-doesnt conduct electricity
high melting point

Question 16

what are some properties of graphite

Answer 16

-each carbon atom forms 3 covalent bonds
-soft and slippery as it is arranged in layers which dont have bonds between them
conducts electricity
-high melting point

Question 17

what are some properties of graphene

Answer 17

it is one layer of graphite
-one atom thich

Question 18

what are some properties of fullerene

Answer 18

-made of carbons shaped like a ball
-they can trap an atom inside
-they can be used to deliver a drug

Question 19

what are some properties of metallic compounds

Answer 19

strong electrostatic forces
-high melting point
-layers can slide, malleable
-good conductors of electricity and heat

Question 20

how to calculate the molecular formula

Answer 20

-calculate Mr of the empirical formula
-divide it by the Mr given
-times that to the formula

Question 21

what is the avogadro constant

Answer 21

6.02*10^23

Question 22

what does the avogadro constant represent

Answer 22

the number of atoms in a mole

Question 23

what is the formula for moles

Answer 23

mass/Mr

Question 24

what is the formula for concentration

Answer 24

mass/volume

Question 25

how to work out empirical formula

Answer 25

-work out amount of moles for each substance
-do the mole ratio to get the number which will then go in the formula

Question 26

how do you calculate the limiting reactants of a reaction

Answer 26

-work out moles of each substance
-divide it by the smaller number
-then the smaller number is the limiting reactant