Amount of substances

Question 1

what is relative atomic mass

Answer 1

Therelative atomic mass(Ar) of an element is the weighted average mass of all its naturally occurring isotopes

Question 2

what is relative formula mass

Answer 2

The relative formula mass (Mr) of a compound is the sum of the relative atomic masses of all the atoms in the compound’s formula unit

Question 3

how do u calculate the relative atomic mass ar

Answer 3

Multiply each isotope’s relative isotopic mass by its isotopic abundance.

Sum these quantities.

Divide by the sum of the isotopic abundances.

Question 4

what does the y and x axis show in the mass spectrum

Answer 4

the y axis shows the percentage abundance and the x axis shows the mass/charge

Question 5

how do you calculate the relative formula mass

Answer 5

Step 1: Write down the molecular formula

H2O

Step 2: Multipy each element’s atom count by its Ar

H: 1.0 × 2 = 2.0

O: 16.0 × 1 = 16.0

Step 3: Calculate Mr

Relative molecular mass = 2.0 + 16.0 = 18.0

Question 6

what is a mole

Answer 6

Themoleis a convenient unit that allows us to count extremely large numbers of atoms and molecules.

Question 7

what is the avogadros connstant ( and the number )

Answer 7

Avogadro’s constanthas a value of6.02 x 1023. This very large number represents how many particles are contained in one mole.

Question 8

what is the triangle that links avogadros constant no.of particles and number of moles

Answer 8

no.of moles = no.of particles / avogadro cons.

Question 9

what is the molar mass

Answer 9

Themolar mass(M) represents the mass in grams of 1 mole of a given substance.

Question 10

what is the triangle that links mass in g molar mass and no. of moles

Answer 10

no.moles=mass in g / molar mass

Question 11

what is the unit for molar mass

Answer 11

g/mol^-1

Question 12

what is the concentration of a solution measured in

Answer 12

g/dm^-3 or mol/dm^-3

Question 13

what is the equation linking mass,volume and concentration

Answer 13

concentration= mass/ volume

Question 14

what is the equation linking moles,volume and concentration

Answer 14

concentration= moles/ volume

Question 15

how do you convert cm3 to dm3

Answer 15

divide by 1000

Question 16

how do convert dm3 to cm3

Answer 16

multiply by 1000

Question 17

how do you convert g/dm^-3 to mol/dm^-3

Answer 17

Divide the concentration in g dm-3by the Mrof the solute

For example, a 58.5 g dm-3solution of NaCl (Mr= 58.5)= 1.00 mol dm-3

Question 18

how do u convert mol dm-3to g dm-3

Answer 18

Multiply the concentration in mol dm-3by the Mrof the solute

For example, a 2.00 mol dm-3solution of NaCl (Mr= 58.5)= 117 g dm-3

Question 19

what are the assumptions that the ideal gas equation obeys

Answer 19

Gas particles move rapidly and randomly.

The volume of the actual gas particles is negligible compared to empty space between them.

There are no intermolecular attractions or repulsions.

Collisions between particles are elastic - no energy is lost.

The average kinetic energy of particles depends only on their temperature.

Question 20

why does the real gas deviate from these assumptions

Answer 20

because they have weak intermolecular attractions and non negligible volumes

Question 21

what are the names of the two gases that come close to the ideal gas

Answer 21

noble gases like helium and neon because their intermolecular forces are minimal

Question 22

what is the formula for ideal gas

Answer 22

pressure (pa) X volume(m3) = moles of gas X the gas constant X temperature (K)

Question 23

what is teh value for the gas constant

Answer 23

8.31

Question 24

how do u convert kPa to Pa

Answer 24

multiply by 1000

Question 25

how do u convert degree celcius to kelcius

Answer 25

add 273 to the original number

Question 26

how do u convert cm3 to m3

Answer 26

divide 1,000,000

Question 27

what is the empirical formula

Answer 27

The empirical formula gives the simplest whole number ratio of atoms of each element present in a compound.

Question 28

what is the molecular formula

Answer 28

The molecular formula gives the actual number and type of atoms of each element in a molecule.

Question 29

give an example of both empiral and molecular formular

Answer 29

An empirical formula of CH2O as this gives the simplest ratio. A molecular formula of C6H12O6 as this shows the actual numbers of atoms in a glucose molecule.

Question 30

what are the two ways to find the empirical formula

Answer 30

percentage composition combustion data

Question 31

explain how to find the empiraical forrmula from the percentage composition

Answer 31

1. assume that all the percentages are in g 2. then find the number of moles in each molecule 3. find the ratio btw them by dividing everything by the smallest no of moles

Question 32

explain the way from a combustion data

Answer 32

A hydrocarbon sample weighing 2.20 g was completely combusted in oxygen, producing 3.30 g of CO2 and 1.35 g of H2O. Determine the empirical formula of the hydrocarbon. Step 1: Calculate moles of CO2 produced moles of CO2​ =Mr ​mass​=44.03.30​=0.075 mol Step 2: Calculate moles of carbon in the sample Each molecule of CO2 contains 1 atom of carbon. Moles of C atoms = Moles of CO2 = 0.075 mol Step 3: Calculate moles of H2O produced moles of H2​O =Mr ​mass​=18.01.35​=0.075 mol Step 4: Calculate moles of hydrogen in the sample Each molecule of H2O contains 2 atoms of hydrogen. Moles of H atoms = 2 x moles of H2O = 2 x 0.075 = 0.150 mol Step 5: Determine the simplest C : H mole ratio C : H = 0.075 : 0.150 = 1 : 2 Step 6: Write the empirical formula The empirical formula is CH2.

Question 33

what are the ways to calculate the molecular formulae

Answer 33

from the empiral formula and from a hydrated ionic salt

Question 34

how to u calculate the molecular mass fro the empiral formula

Answer 34

1. finding the empiral formula form the question ( calculate the Mr ) 2. then divide the molecular mass by the empiral formula mass 3. the number u get is the number present in the equation basically

Question 35

how do u calculate the molecular formula from the hydrated ionic salt

Answer 35

calculate the mass of water lost them moles of the anydrous thingy lost my dividing mass / Mr then do the same for hydrated ( water) then find the ratio

Question 36

what is the formula to calculate the number of atoms

Answer 36

no.of atoms = amount of substance / moles X avogadro's constant