Basics- Environmental Chemistry

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What is a chemical element?
Pure chemical substance consisting one one type of atom distinguished by its atomic number
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What is a compound?
Where two distinct elements are chemically combined with bonds
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What is an atomic number?
The number of protons in the nucleus of an atom
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What are isotopes?
Versions of the same element .- they have the same number of protons but with varying neutron abundances
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How do you calculate the atomic mass of an atom?
Add together the number of protons and neutrons in the nucleus.
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What is the relative atomic mass of an element?
The average atomic mass of all the chemical's isotopes, weighted by abundance.
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What is a mole?
A unit of measurement to describe the amount of a substance
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What is avagadro's number?
6.0221367 times 10 to the 23
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What is molar mass?
How much in grams 6.02 times 10 to the 23 of a substance "weighs".
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What is Le Chatelier's principle?
If a system is perturbed, the system will react in such a way to minimise the reduced change.
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How do inert elements differ from others?
Tend to be found in the form of atoms. Not combined with other elements.
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Why are some elements inert?
Energetically stable pattern of electrons in the outer shell of the atoms.
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What happens in a colvalent bond?
Outer electrons are shared between 2 atoms so that both gain an "inert element" type structure and are energetically stable.
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What are organic species?
These contain carbon, hydrogen and some non-metallic elements e.g. oxygen, nitrogen, sulphur; or halogens eg. chlorides.
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What are alkanes?
Molecules that are saturated (no double bonds) C(n) H(2n+2)
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What are alkenes?
Unsaturated molecules with no double bonds. C(n) H(2n)
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What are alkynes?
Unsaturated molecules with triple bonds
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What are the prefixes for elements with 1,2,3 and 4 carbons?
Meth, eth, prop, but
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What are inorganic species?
Compounds without carbon and hydrogen.
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How do inorganic materials bond?
Ionic bonding
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What happens in ionic bonding?
The atoms either donate or accept electrons to gain a structure more like inert gases. In doing so they become charged.
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How are ionic compounds held together?
Electrostatic attractions between the charged particles giving an overall neutral charge.
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What is electronegativity?
Tendency of an atom to attract additional electrons
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What sort of bond do atoms with similar electronegativities form?
Covalent
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What are positive ions?
Cations
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What are negative ions?
Anions
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Why do atoms not usually lose/gain more than 3 electons?
Energetically unfavourable. Species bond covalently instead.
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What has happened to form a monovalent compound?
One electron has been donated and accepted
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What happens to form a divalent or trivalent compound?
2/3 electrons have been donated and accepted
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What tends to happen to metals when they form ionic bonds?
They tend to lose electrons as they are in groups 1-3 on the periodic table. They therefore lose negative charge and become cations
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What tends to happen to non-metals when they form ionic bonds?
They tend to gain electrons as they have either 1,2 or 3 less electrons than needed to have a full outer shell and become energetically stable. They therefore become anions.
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What is the standard unit for water chemistry?
mol l(-1)
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What is a milli mol?
10(-3)
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What is a micro mol? (the one that looks like a u shape)
10 (-6)
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What is molarity?
The number of moles of a given substance per litre of solution.
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What is an acid?
A substance that dissociates in water to yield hydrogen ions or gains electrons from electrons from the 0H- ion in water.
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What are bases?
Alkalis- substances which yield OH- in solution.
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Acid+base= ?
Dissolved salt +water
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Why might the arrow in a reaction for acid+base be reversible?
If the acid and base are weak they may dissociate only partly in water
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Examples of weak acid/base?
Weak acid- Formic (HCOOH); Weak base- Ammonium hydroxide (NH4OH)
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What does the pH scale describe?
The acidity of solutions
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How does pOH relate to pH?
pH=14-pOH
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What is the pH when H+=OH-?
7 (neutral)
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In natural waters what is the pH influenced by? Where do these compounds originate from?
CO2 (decomposition), SO2(volcanic gases) and NO (electric discharge e.g. lightning)
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What activity might add additional NO to the environment?
Internal combustion e.g driving cars
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What activity might add additional S02 to the environment?
Fossil fuel combustion-mainly coal, some oil.
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How do you work out H+ ion concentration from pH?
pH=-log10{H+}
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If pH=2, what is the concentration of H+ in mol l-1?
1 times 10 (power-2)
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If pH=4, what is the concentration of H+ in mol l-1?
1 times 10 (power-4)
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If pH=2, what is the concentration of OH- in mol l-1?
1 times 10 (power-12)
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How do you work out the concentration of OH- ions from pH?
14-pH. Then -log10[previous answer]
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How would you find the number of moles in a chemical substance?
Either mass divided by Mr. Or Concentration times volume.
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How would you find the mass of a chemical substance?
Number of moles times Mr.
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What equation would you use to find the volume of a substance?
Number of moles divided by concentration
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What are the units for M?
1 mol/L = 1M
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Other cards in this set

Card 2

Front

What is a compound?

Back

Where two distinct elements are chemically combined with bonds

Card 3

Front

What is an atomic number?

Back

Preview of the front of card 3

Card 4

Front

What are isotopes?

Back

Preview of the front of card 4

Card 5

Front

How do you calculate the atomic mass of an atom?

Back

Preview of the front of card 5
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