unit 1 section 2 Amount of Substance

Question 1

what is Avogadros constant

Answer 1

6.022x10^23

Question 2

how to work out the number of particles

Answer 2

number of particles = moles x avogadros

Question 3

what is the equation for the ideal gas equation

Answer 3

P x V = N x R x T
p = pressure (pa )
v = volume ( m^3)
n= number of moles
r = gas constant ( 8.31)
t = temperature ( k )

Question 4

how do you convert Kpa to pa

Answer 4

x 1000

Question 5

how do you convert degrees into kelvin

Answer 5

you add 273

Question 6

how do you convert cm^3 to m^3

Answer 6

divide by 10^6 or you times it by 10^-6

Question 7

how do you convert dm^3 to cm^3

Answer 7

x10^3

Question 8

how do you write ionic equations

Answer 8

first you write the full balanced equation and then you split it up into their ions and you remove any ions that appear on both sides.

Question 9

what do you get when an acid reacts with a alkali

Answer 9

salt + water

Question 10

what is a standard solution

Answer 10

it is any solution you know the concentration of

Question 11

how do you make a standard solution

Answer 11

you dissolve a known amount of solid into a know amount of water

Question 12

how to carry out a titration

Answer 12

1 - pipette a set volume of solution you want to know the concentration of. and add a few drops of indicator
2- fill up the burette with a standard solution of acid, you a funnel to pour in acid.
3- then you do a rough titration to get an idea of the end point of the reaction.
4- then you do an accurate titration, run acid within 2cm^3 of end point and then add acid dropwise while swirling the solution until the solution is neutralised and work out the titre by subtraction the final reading by the initial reading.
5- repeat the test a few times until you have at least 3 concordant results.

Question 13

what are concordant results

Answer 13

they are results that are within 0.1 cm^3 of each other

Question 14

what is empirical formula

Answer 14

it is the smallest whole number ratio of atoms of each element in a compound

Question 15

what is the molecular formula

Answer 15

it is the actual number of atoms in a molecule.

Question 16

how to calculate molecular formula from the empirical formula and mr

Answer 16

1- find the empirical mass(mr) of the compound.
2- divide the mr by the empirical mr
3- multiply the empirical formula by the number you got.

Question 17

how do you work out the empirical formula for the percentages of the elements present

Answer 17

1- assume 100g of compound, work out the moles of each element with the percentages as grams.
2 - divide each number of moles by the smallest number of moles you find in step 1
3- apply those number to the formula ( numbers must be whole numbers )

Question 18

what is the theoretical yield

Answer 18

it is the mass of a product that should be formed in a chemical reaction.

Question 19

what is the actual yield

Answer 19

it is the mass of product that is produced in the reaction.

Question 20

what is the equation for percentage yield

Answer 20

percentage yield = actual yield / theoretical yield x100

Question 21

what is atom economy

Answer 21

it is the measure of the proportion of reactant atoms that become part of the desired products in the balanced chemical equation

Question 22

what are the economic advantages of high atom economy

Answer 22

• company has more efficient use of raw materials
• company will have less waste to deal with , means less money is spent on disposing waste safely and less time is spent separating desired product from waste product.

Question 23

what are the environmental and ethical advantages of using high atom economy

Answer 23

• limited supply of raw materials , means they last longer when used efficiently
• less waste - less harmful chemicals which are difficult to dispose.
• more sustainable

Question 24

what is the equation for atom economy

Answer 24

atom economy = molecular mass of desired product / total molecular mass of reactants x 100

Question 25

how do you convert mPa to Pa

Answer 25

x1,000,000
x 1 million