Formulae , Equations and Amounts of substance

Question 1

Equations for the number particles

Number of particles = …

Answer 1

Number of particles = Avogardo number * moles

Question 2

Equation for moles

Moles=…

Answer 2

Moles= Mass/RFM

Question 3

Equation for number of moles

involving concentration and volume

Answer 3

Number of moles = concentration * volume

Question 4

Equation for moles

includes volume and molar gas volume

Answer 4

Moles = volume / molar gas volume

Question 5

Equation for concentration

includes mass and volume

Answer 5

Concentration = mass * volume

Question 6

What’s the equation for ideal gas ?

Answer 6

pressure * volume = molesgas constant temperature

PV= nRT

Question 7

What’s the equation for percentage error ?

Answer 7

Percentage error = uncertainty / reading * 100

Question 8

What’s the equation for percentage yield ?

Answer 8

Percentage yield = actual yield / theoretical yield * 100

Question 9

What’s the equation for % atom economy

Answer 9

% atom economy = Molecular mass of desired product / sum of molecular mass of all reactants * 100

Question 10

What does the % atom economy tell us about the reaction

Answer 10

It tells us how efficient the reaction is

Question 11

what is volume of 1 mole of gas

Answer 11

24 litres

Question 12

What is Avogadro’s constant ?

Answer 12

6.02 x 10*23

Question 13

What is a limiting reagent?

Answer 13

The one that runs out first

Question 14

A+B -> C
moles of A = 1
moles of B = 2
What the moles of C and what’s the limiting reagent and what’s in excess ?

Answer 14

C=1 , A is the limiting reagent and B excess with 1 mole being left

Question 15

3A + 2B -> 2C
moles of A = 3
moles of B = 3
What’s C and what’s the limiting reagent and what’s in excess ?

Answer 15

ratio between A and C of 3:2
divide A by 1.5 , C = 2
B is limiting and A is excess

Question 16

What equation do you use when you have conc and vol before and after the reaction ?

Answer 16

Conc 1 * vol 1 = conc 2 * vol 2

Question 17

What’s a titration and when would you use a titration ?

Answer 17

A titration is used to find a unknown concentration of solution by reacting it with a reactant with a known concentration

Question 18

What is the empirical formula ?

Answer 18

The empirical formula is the smallest whole number ratio of the atoms of each element in a compound

Question 19

Describe how you would find the empirical formula of a compound that has 27.3% carbon and 72.7% oxygen (mass)

Answer 19

1. divide carbon by its % and RFM and do the same with oxygen
   C = 27.3 / 12 = 2.3 , O = 72.7/16 = 4.5
2. Divide each number by the smallest number
   C= 2.3/2.3 =1 , O = 4.5/ 2.3 = 2
3. this the ratio of the two numbers in the compound
   CO2

Question 20

What’s the molecular formula

Answer 20

shows the actual numbers of the atoms of each elements

Question 21

What are spectator ions ?

Answer 21

Ions in an iconic compound that do not take part in a reaction

Question 22

What are the steps for simplifying full iconic equations ?

Answer 22

1. Start with the full equation
2. Replace the formulae of ionic compound by their separate ions
3. Cancel out any ions that appear identically on both sides

Question 23

What is Avogadro’s law ?

Answer 23

States that equal volumes of gases under the same conditions of temperature and pressure contain the same numbers of molecules

Question 24

Describe a outline of a titration

Answer 24

1. Add the acid to the alkali until the equivalence point ( the point at which there are exactly the right amounts of substances) of the titration and the end point (the point where the indicator just changes colour ) has been reached
2. Record the lowest part of the meniscus
3. Record the titre
4. repaet the titration until concordant titres are obtained

Question 25

what is the meniscus ?

Answer 25

the curving of the upper surface in a liquid in a container , should read the lowest part of the meniscus

Question 26

What is a titre ?

Answer 26

the volume added from the burette during a titration

Question 27

What is the concordant titres ?

Answer 27

titres that are close together ( usually titres of 0.1 - 0.20 cm3)

Question 28

What is a precipitation reaction ?

Answer 28

reactions in which an insoluble soild is one of the products

Question 29

What are the 5 equations for the reactions between acid and metals ?

Answer 29

1. Metal + acid -> salt + hydrogen
2. Metal oxide + acid -> salt + water
3. Metal hydroxide + acid -> salt + water
4. Metal hydroxide + acid -> salt + water
5. Metal carbonate + acid -> salt + water + carbon dioxide

Question 30

What happens when a metal hydrogen carbonate reacts with a acid ?

-Use the example of sodium hydrogencarbonate and citric acid

Answer 30

Sodium hydrogencarbonate + citric acid -> sodium citrate + water + carbon dioxide

Question 31

Define accuracy

Answer 31

A measure of the closeness of agreement between an individual result and the accepted value

Question 32

Definition of precision

Answer 32

The closeness of the values obtained between independent measurements obtained under the same conditions

Question 33

Definition of uncertainty

Answer 33

An estimate attached to a measurement based on range the true value could be in

Question 34

Definition of reliability

Answer 34

The opposite of uncertainty , high uncertainty = not very reliable