inorganic and physical chemistry

Question 1

how do you write ionic equations

Answer 1

1. balance the equation
2. separate the soluble compounds into ions
3. leave insoluble compounds as they are
4. balance the charges on each side and balance the number of atoms

inc state symbols

Question 2

what are the common ionic equations

Answer 2

1. acid + hydroxide –> water
2. acid + carbonate –> water + carbon dioxide
3. acid + hydrogen carbonate –> water + carbon dioxide
4. acid + ammonia –> ammonium

Question 3

what is the relative mass of an electron

Answer 3

1/1836

Question 4

define an atom

Answer 4

the smallest particle of a chemical element that can exist

Question 5

define an element

Answer 5

a substance that contains only 1 type of atom, which all have the same number of protons

Question 6

define relative atomic mass

Answer 6

the weighted mean mass of one atom of an element relative to 1/12 of the mass of carbon-12.
- it is an average of all the mass numbers of all the different isotopes of that element

Question 7

how does a time of flight spectrometer work

Answer 7

1. place the sample in the spectrometer
2. sample is then vaporised and then ionised to form positive ions
3. ions are accelerated (heavier ions move slower and are harder to deflect than lighter ones, this separates ions of each isotope)
4. the ions are detected on a mass spectrum as an m/z ratio ( mass to charge) each ion that reaches the detector adds to the signal, therefore the greater the abundance, the larger the signal

Question 8

define a compound

Answer 8

a substance composed of 2/more separate elements

Question 9

define a molecule

Answer 9

a group of atoms bonded together representing the smallest fundamental unit of a chemical compound that can take part in a chemical reaction

Question 10

what are polyatom ions

Answer 10

gain or lose elemental ions such as a proton

Question 11

what is molar mass

Answer 11

mass per mole of a substance in gmol-1

Question 12

what is an empirical formula

Answer 12

simplest whole number ratio of atoms of each element in a compound

Question 13

how do you calculate empirical formula

Answer 13

1. what’s the mass??
2. no. moles
3. divide each no. moles by the smallest mole value to get a ratio
4. adjust the numbers to make them a whole number
5. write the empirical formula

Question 14

what is ‘water of crystallisation’

Answer 14

water molecules that are bonded into a crystalline structure of a compound

Question 15

define hydrated

Answer 15

crystallised compound containing water molecules

Question 16

define anhydrous

Answer 16

contains no waters of crystallisation

Question 17

what does ‘SnCl4 . 8H2O’ mean

Answer 17

8 H2O molecules per 1 SnCl4

Question 18

when completing the crystallization practical, why could your value be lower

Answer 18

all the water was not lost so less water was released

Question 19

when completing the crystallization practical, why could your value be higher

Answer 19

salt begins to decompose so more mass lost

Question 20

how can you work out the new concentration of something

Answer 20

(o.g vol/new vol)* o.g conc

Question 21

what is avogadro’s law

Answer 21

equal volumes of gases under the same temp and pressure contain the same number of molecules , therefore 1 mole of any gas occupies the same vol. at a certain temp and pressure

Question 22

what is room pressure

Answer 22

1 atmosphere = 101 Pa

Question 23

what is room temperature

Answer 23

25 Celsius = 298 kelvin

1 kelvin = 1 degree Celsius

Question 24

what is the ideal gas equation

Answer 24

pV=nRT

p = pressure (Pa)
V = volume (m^3)
n = number of moles
R = gas constant (K-1mol-1)
T = temperature (K)

Question 25

what is the gas constant

Answer 25

8.3140

Question 26

what is an ideal gas

Answer 26

any gas that obeys avogadro’s under all conditions

Question 27

how can you determine the Mr of a gas

Answer 27

1. place gas cylinder on balance and record mass
2. release sample of gas into a syringe ( syringe at same pressure as surrounding air)
3. reweigh the gas cylinder so mass in syringe can be calculated
4. find the temp, read vol, calc mass, use gas constant, record room pressure and use pV=nRT and rearrange to find mol
5. use mol and mass to calc Mr