section 1 Principles of chemistry part 2 Flashcards
what are isotopes?
Different atomic forms of the same element
With the same number of protons
But different number of neutrons
what is the equation for relative atomic mass?
(rel. mass x rel. abundance of isotope 1) + (rel. mass x rel. abundance of isotope 2) / the sum of the rel. abundances
what is the relative formula mass of H2O?
2 + 16 = 18
what is the empirical formula?
smallest whole number ratio of atoms in a compound
what is the molecular formula?
actual number of atoms in a compound
what is Avogadro constant?
moles 6.023x10(23)
whats the equation for number of moles?
mass in g divided by the relative formula mass
what is a solid salt containing water of crystallization?
hydrated
what is an anhydrous salt?
a salt without water of crystallization
what are the 2 equations to find volume using mole?
volume = moles of gas x 24 volume = (mas of gas/ relative formula mass) x100
what is concentration measured in?
moles per dm3
what is the equation for concentration?
number of moles/volume
electric current is ………………………
A flow of electrons or ions
when do ionic compounds conduct?why?
molten or in solution
electrons free to move
do covalent compounds conduct electricity?
no
why are metals good conductors?
they have a sea of delocalised electrons to carry an electrical current
why are metals malleable?
layers of atoms can slide over each other
electrolysis is used to …………………..
make new substances
what is an electrolyte?
a liquid that conducts electricity
what is the name of the positive rod?
anode
what is the name of the negative rod?
catode
which way do the electrons flow?
from the anode (+) to the cathode (-)
how many coulombs of charge is a faraday?
96 500
What is avogadros law?
One mole of any gas occupies 24dm3 at room temperature and pressure
What are the two equations for volume in dm3?
Moles of gas x 24
Mass of gas / Mr of gas x 24
How do you calculate the volumes in a reaction if you know the masses?
Find the reacting mass
Use the formula to find the volume
What happens in electrolysis of aqueous solutions?
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
What happens in the electrolysis of sulfuric acid?
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-
What happens in the electrolysis of sodium chloride?
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-
What happens in the electrolysis of copper sulfate?
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-
How can the number of electrons transferred in electrolysis (to therefore increase the yield) be increased?
Electrolysing for a longer time
Increasing the current
One faraday contains
One mole of electrons
96500 coulombs is
One faraday
What is the equation for charge
Current x time
I x t
How do you calculate the masses for electrolysis?
- Write out the balanced half-equation for the reaction at the electrode with the element you want
- Calculate the faradays (Q / 96500) by calculating the charge (Q = I x t) first
- 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)
- 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).
What does oxidised mean?
Loss of electrons.
What does reduced mean?
Gain of electrons.
What does a redox reaction mean?
When oxidation and reduction has both happened equally.
The breaking of bonds is …………
And the making of bonds is …………
Endothermic
Exothermic.
What are the 3 steps for calculating masses?
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
What is the equation for percentage yield?
Actual yield(grams)/ theoretical yield(grams) x 100
What is room temperature and pressure?
25 degrees
1 atmosphere
