section 1 Principles of chemistry part 2

Question 1

what are isotopes?

Answer 1

Different atomic forms of the same element
With the same number of protons
But different number of neutrons

Question 2

what is the equation for relative atomic mass?

Answer 2

(rel. mass x rel. abundance of isotope 1) + (rel. mass x rel. abundance of isotope 2) / the sum of the rel. abundances

Question 3

what is the relative formula mass of H2O?

Answer 3

2 + 16 = 18

Question 4

what is the empirical formula?

Answer 4

smallest whole number ratio of atoms in a compound

Question 5

what is the molecular formula?

Answer 5

actual number of atoms in a compound

Question 6

what is Avogadro constant?

Answer 6

moles 6.023x10(23)

Question 7

whats the equation for number of moles?

Answer 7

mass in g divided by the relative formula mass

Question 8

what is a solid salt containing water of crystallization?

Answer 8

hydrated

Question 9

what is an anhydrous salt?

Answer 9

a salt without water of crystallization

Question 10

what are the 2 equations to find volume using mole?

Answer 10

volume = moles of gas x 24
volume = (mas of gas/ relative formula mass) x100

Question 11

what is concentration measured in?

Answer 11

moles per dm3

Question 12

what is the equation for concentration?

Answer 12

number of moles/volume

Question 13

electric current is ………………………

Answer 13

A flow of electrons or ions

Question 14

when do ionic compounds conduct?why?

Answer 14

molten or in solution

electrons free to move

Question 15

do covalent compounds conduct electricity?

Answer 15

no

Question 16

why are metals good conductors?

Answer 16

they have a sea of delocalised electrons to carry an electrical current

Question 17

why are metals malleable?

Answer 17

layers of atoms can slide over each other

Question 18

electrolysis is used to …………………..

Answer 18

make new substances

Question 19

what is an electrolyte?

Answer 19

a liquid that conducts electricity

Question 20

what is the name of the positive rod?

Answer 20

anode

Question 21

what is the name of the negative rod?

Answer 21

catode

Question 22

which way do the electrons flow?

Answer 22

from the anode (+) to the cathode (-)

Question 23

how many coulombs of charge is a faraday?

Answer 23

96 500

Question 24

What is avogadros law?

Answer 24

One mole of any gas occupies 24dm3 at room temperature and pressure

Question 25

What are the two equations for volume in dm3?

Answer 25

Moles of gas x 24

Mass of gas / Mr of gas x 24

Question 26

How do you calculate the volumes in a reaction if you know the masses?

Answer 26

Find the reacting mass

Use the formula to find the volume

Question 27

What happens in electrolysis of aqueous solutions?

Answer 27

Cathode: If H+ ions and metal ions are present, hydrogen gas will be produced if the metal ions are more reactive than the H+ ions, if the metal ions are less reactive, a solid layer of the pure metal will be produced

Anode: if OH- and halide ions are present, then those molecules will be formed, if not oxygen will form

Question 28

What happens in the electrolysis of sulfuric acid?

Answer 28

Contains SO4(2-), H+2, OH- ions

Hydrogen ions accept electrons so at the cathode hydrogen is produced: 2H+ + 2e- ➡️H2

Hydroxide ions lose electrons more easily than sulfate ions, so at the anode oxygen and water are produced: 4OH- ➡️ O2 + 2H2O + 4e-

Question 29

What happens in the electrolysis of sodium chloride?

Answer 29

Contains Na+, Cl-, OH-, H+

Hydrogen ions accept electrons so hydrogen gas is produced at the cathode: 2H+ + 2e- ……… H2

Chloride ion lose electrons more easily than hydroxide ions so chlorine gas is produced: 2Cl- ……… Cl2 + 2e-

Question 30

What happens in the electrolysis of copper sulfate?

Answer 30

Contains Cu+2, SO4(2-), H+, OH-

Copper ions accept electrons more easily than hydrogen ions so at the cathode copper metal is produced: Cu+2 + 2e- ……. Cu

Hydroxide ions lose electrons more easily than sulfate ions so at the anode oxygen and water are produced: 4OH- ……… O2 + 2H2O + 4e-

Question 31

How can the number of electrons transferred in electrolysis (to therefore increase the yield) be increased?

Answer 31

Electrolysing for a longer time

Increasing the current

Question 32

One faraday contains

Answer 32

One mole of electrons

Question 33

96500 coulombs is

Answer 33

One faraday

Question 34

What is the equation for charge

Answer 34

Current x time

I x t

Question 35

How do you calculate the masses for electrolysis?

Answer 35

1. Write out the balanced half-equation for the reaction at the electrode with the element you want
2. Calculate the faradays (Q / 96500) by calculating the charge (Q = I x t) first
3. Calculate the number of moles produced (One mole = one f, but be careful as look at how many electrons are added in half equation, if 2 or any number apart from one, divide faradays by 2 or that number to get no of moles)
4. Write in the Mr values from the periodic table to work out the mass (m = n x Mr) (Mr is the top number on each element of the periodic table).

Question 36

What does oxidised mean?

Answer 36

Loss of electrons.

Question 37

What does reduced mean?

Answer 37

Gain of electrons.

Question 38

What does a redox reaction mean?

Answer 38

When oxidation and reduction has both happened equally.

Question 39

The breaking of bonds is …………

And the making of bonds is …………

Answer 39

Endothermic

Exothermic.

Question 40

What are the 3 steps for calculating masses?

Answer 40

Wrote the balanced equation
Work out Mr of bits you want and divide them by the balancing number in the equation
Divide to get one then multiply to get all

Question 41

What is the equation for percentage yield?

Answer 41

Actual yield(grams)/ theoretical yield(grams) x 100

Question 42

What is room temperature and pressure?

Answer 42

25 degrees

1 atmosphere