Section 1: Principles of Chemistry Flashcards
What is the definition of diffusion?
The net movement of particles from an area of higher concentration to an area of lower concentration
What increases the rate of diffusion?
Higher energy and lower mass of particles
Which two solutions are used in the experiment to test how density of particles affects rate of diffusion?
Hydrochloric acid (HCl) and ammonia solution (NH4)
Are ammonia particles heavier than hydrochloric acid particles?
no
What is the white substance formed when hydrochloric acid and ammonia react?
Ammonium chloride
In the experiment testing how the density of particles affects the rate of diffusion, does the white ring form closer to the hydrochloric acid or ammonia solution?
Hydrochloric acid
What is the experiment to show diffusion occurring in air?
Bromine in a gas jar
What is the definition of an atom?
the smallest particle of an element
What is the definition of a molecule?
Two or more non-metal atoms held together by covalent bonds
What is the definition of an element?
a pure substance made of only one kind of atom
what is the definition of a compound?
A substance containing two or more elements bonded together in a fixed ratio
what is the definition of a mixture?
a combination of two or more substances that are not chemically combined
what is filtering used to separate?
Insoluble particles from a liquid (e.g. sand from water)
What is evaporation used to separate?
Dissolved substances from a solution (e.g. salt from a salt solution)
What is simple distillation used to separate?
The liquid from a dissolved solid in a solution (e.g. water from a salt solution)
What is fractional distillation used to separate?
Liquids from a mix of liquids (e.g. alcohol from a mix of alcohol and water)
What is chromatography used to separate?
A mixture of soluble substances (e.g. the colours found in ink)
What is crystallisation used to separate?
Solids from a solution (when hot solution is left to stand, allowing crystals to form)
What do chromatographs show?
How many different substances in a substance and their relative solubility (the most soluble solvent will travel the furthest)
What is the relative charge of a proton?
+1
What is the relative mass of a proton?
1
what is the relative charge of an electron?
-1
what is the relative mass of an electron?
1/1840
what is the relative charge of a neutron?
0
what is the relative mass of a neutron?
1
what is found in an atoms central nucleus?
protons and neutrons
how many electrons are in the first shell?
2
how many electrons are in the second shell?
8
how many electrons are in the third shell?
8
where are electrons found in an atom?
orbiting the nucleus in shells
what is the definition of atomic number?
the number of protons in the nucleus of an atom
what is the definition of mass number?
the total number of protons and neutrons in the nucleus of an atom
what is the definition of an isotope?
atoms of the same element with a different number of neutrons
what is the definition of relative atomic mass (Ar)?
the average mass of the atoms of an element
How do you calculate the relative atomic mass?
∑(isotope mass x isotope abundance) ÷ 100
what is the periodic table?
an arrangement of elements in order of atomic number
What does a group in the periodic table tell you about the element?
The number of electrons in the element’s outer shell and the charge of the elements ion
What is the charge on an ion of an element in group 2?
+2
What is the charge on an ion of an element in group 7?
-1
What does a period in the periodic table tell you about the element?
The number of shells with electrons in and element has
what is formula mass?
the sum of the atomic masses of all the atoms in the compound
what are moles?
The Avogadro number of particles in a substance (represents the amount of substance)
what is the formula to calculate moles from mass and formula mass?
Moles = mass ÷ formula mass
What is the molar volume of gas?
24 dm3 or 24,000 cm3
what is the formula to calculate moles from volume?
Moles = volume ÷ 24dm3
What is the state symbol for solids?
(s)
what is the state symbol for liquids?
(l)
what is the state symbol for gases?
(g)
what is the state symbol for aqueous solutions?
(aq)
How do you calculate the formula of a hydrated substance?
- Work out formula (using x to represent the number of water molecules)
- Work out mass of water and mass of substance (weigh before and after heating)
- Use formula to calculate moles
- Work out simplest ration by dividing both numbers by the smallest
what is the empirical formula?
The simplest whole number ratio of atoms of each element present in a compound
How do you work out empirical formula?
- Divide mass of substances by relative atomic mass for each substance
- Simplify ratio by dividing each number by the smallest one
what is the formula for working out molecular formula from molecular formula mass and empirical formula?
(Molecular FM ÷ empirical FM) x empirical formula
How do you calculate reacting masses?
- Work out moles of substance whose mass has been given
- Work out moles of other substance using ratio of the two
- Calculate mass of other substance by multiplying moles by FM
what is the formula for calculating the percentage yield?
(Actual amount of product produced ÷ theoretical amount of product produced) x 100%
what is the formula for calculating moles using volume and concentration?
Moles = volume (dm3) x concentration (mol/dm3)
what is oxidation (in the context of electrons)?
loss of electrons (OIL)
what is reduction (in the context of electrons)?
gain of electrons (RIG)
nitrate ion
NO₃¹⁻
sulfate ion
SO₄²⁻
carbonate ion
CO₃²⁻
hydrogen carbonate ion
HCO₃¹⁻
hydroxide ion
OH¹⁻
phosphate ion
PO₄³⁻
ammonium ion
NH₄¹⁺
silver ion
Ag¹⁺
zinc ion
Zn²⁺
lead ion
Pb²⁺
aluminium ion
Al³⁺
what is an ionic bond?
the strong electrostatic attraction between oppositely charged ions
Why do ionic compounds have high melting and boiling points?
A lot of energy is required to break the strong ionic bonds between particles
How does charge affect the melting/ boiling point of an ionic compound?
The greater the charge, the greater the electrostatic attraction, the stronger the ionic bond, the more energy required to break that bond, the higher the melting/ boiling point
Why are ionic compounds soluble in water?
Water is polar molecule so the positive side attracts the negative ions and vice versa, breaking up the ionic lattice
Why don’t ionic compounds conduct electricity?
When the ions are locked into a lattice the cannot move and carry charge
Why do ionic compounds conduct electricity when molten or dissolved?
The ionic lattice is broken up so the ions can flow and carry charge
Why are ionic compounds brittle?
If like charges are forced together they are repelled away from each other
what is an ionic crystal?
A giant 3D lattice structure held together by the attraction between oppositely charged ions
How are covalent bonds formed?
by the sharing of electrons between two atoms
what is a covalent bond?
A strong electrostatic attraction between the binding pair of electrons and the nuclei of the atoms involved in the bond
what can simple molecular structures be?
Non-metal elements (e.g. oxygen)
Non-metal compounds (e.g. carbon dioxide)
Carbon in the form of Buckminster Fullerene
Why do simple molecular structure have low melting and boiling points?
They have relatively weak inter-molecular forces which do not require much energy to be overcome/broken
Why don’t simple molecular structures conduct electricity?
they don’t have an overall charge
what are allotropes?
the same elements with different molecular structures
Why do giant covalent structure have high melting points?
A large amount of energy is required to break the strong covalent bonds
Why are giant covalent structures insoluble?
In order to dissolve the structure would have to be broken up and the covalent bonds require too much energy to be broken
Why don’t giant covalent structures conduct electricity?
The electrons in the outer shell are held tightly in covalent bonds so are not free to move and carry charge
What is diamond used for?
Used for cutting as it is very hard due to the strong covalent bonds
Why does graphite conduct electricity?
The delocalised electrons can flow and carry charge
What is graphite used for?
As a lubricant because the attraction between each layer of graphite is relatively weak so can easily be flaked off
what is a metal structure?
A giant structure of positive ions surrounded by a sea of delocalised electrons
Why can metals conduct electricity?
Delocalised electrons can flow and carry charge
Why are metals malleable?
Layers of positive ions can slide over one another
Why do metals have high melting and boiling points?
Strong electrostatic forces require a lot of energy to be broken
what is a metallic bond?
Strong electrostatic attraction between positively charged ions and the delocalised electrons
what is electric current?
the flow of charged particles (ions or electrons)
what is an electrolyte?
a substance that undergoes electrolysis (always contains ion)
is an anode positive or negative?
positive
is a cathode positive or negative?
negative
are anions negative or positive?
negative
are cations negative or positive?
paw-sitive
do anions flow to the cathode or anode?
anode
at the anode if the ion is a halogen what is formed?
the halogen
At the anode if the ion is not a halogen what is formed?
Oxygen from OH- ions
what is the ionic half equation for the formation of oxygen from hydroxide ions?
4OH- —> 2H2O + O2 + 4e-
What is formed at the cathode if the cation is more reactive than hydrogen?
hydrogen gas
What is formed at the cathode if the cation is less reactive than hydrogen?
The metal (copper/silver/gold) is formed
What three metals are less reactive than hydrogen?
Copper, silver, gold
What does one faraday represent?
The charge on one mole of electrons (96,500c)
Describe how crystallisation can be used to obtain a pure dry sample of a salt
1) heat solution until crystals start to form
2) allow to cool/crystallise
3) filter and wash with water
4) leave to dry
Explain how particle theory can be used to explain brown colour filling a gas jar with liquid bromine at the bottom
1) the bromine liquid evaporates
2) bromine has fills the gas jar because the gas particles move randomly
What colour is magnesium oxide?
White
What colour is copper oxide?
Black
What does cobalt chloride do in the presence of water?
Turns from blue to pink
Why is the solvent level in chromatography experiments below the base line?
To prevent ink spots dissolving in the solvent
explain in terms of its structure why graphite can act as a lubricant
1) layers can slide over each other
2) weak intermolecular forces of attraction between layers
explain why buckminsterfullerene has a much lower melting point than diamond
1) Not a giant structure
2) Weak intermolecular forces of attraction
3) No covalent bonds break when melting
what is electrolysis?
the decomposition of a molten or aqueous ionic substance by electricity
suggest why, in an electrolysis when the copper electrodes take part in the reaction, the increase in mass of the negative electrode is less than expected
1) some copper did not stick to negative electrode/cathode
2) some copper removed during washing/drying
3) positive electrode/anode impure
