Energy and Environment 7

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What is an acid?
Acid is something which produces hydrogen ions (H+) in water. h3O+ is a hydronium ion, or H+. ie - HCl+H2O-> h3O+ +Cl-
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What is a base?
Base produces hydroxide ions in water: NaOH-> Na+ +OH-
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What is ka?
Ka is dissociation constant. Stronger acid has higher dissociation constant. pka= -log10ka. pH=-log[H3O] (Mols/litre )
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What is acid dissociation constant?
ka = [H3O+]*[A-]/[HA] where H3O is the hydronium, A- is the salt, and HA is the acid. All mols/litre
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What are buffer solutions?
Buffer solutions resist change to pH when a small amount of base/acid is added. Consist of salt and weak acid. (Salt is A- and weak acid HA). It exploits Le Chatelier's principle (ie adding H3O+ will result in reaction shifting to left
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Why is metal in water a problem? What metals are there to remove?
Metal is toxic to aquatic life. Metals to remove: Pb, Cu, Cr, Fe, Mn, Hg, Ni, and Zn
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How can we remove soluble metal ions?
To remove soluble metal ions we commonly precipitate them as hydroxide. By raising pH with alkaline such as lime, insoluble metal hydroxides form
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Give an example of a precipitate reaction with zinc?
Zn(OH)2 <-> Zn2+ + 2OH- increasing hydroxide concentration makes reaction move to the left, removing zinc from solution and resulting in zinc hydroxide. Metal solubility falls with pH
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what are concentration and molarity?
Concentration is amount of solute in solution. (mg/L) Molarity = mols/l
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We have 45g of NaCl in 1 litre of water. What's its molarity?
If we have 45 g Nacl in 1 litre of water, looking at molecular mass it is 58.5. So to find molarity in 1l of water, we divide 45 by 58.5=0.789 mols/litre
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What is normality?
Normality, N= equivalent of solute/1 litre of solution (Basically mass for 1 positive or negative charge per litre of water)
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What is formula for equivalent?
Equivalent = molecular mass/ion charge
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For water data, we have the amounts of components such as Ca 2+ etc, how can we find if the charges are equal?
Sum the cation and anion charges. Divide molecular weight by charge (Equivalent) and then divide weight in water (ie we have 2.9mg of Ca2+) by the equivalent (ie- 2.9/20) to get the weight per charge for that substance. Anion and cation totals same
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What is Henry's law?
Henry's law defines amount of gas in water. [X(aq)] (amount of dissolved gas, mol/litre) = k*Px (Px is partial pressure, atm)
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What does solubility of gases in water rely on?
Solubility of gases drops with temperature. Solubility of gases relies on water temperature, partial pressure, and salt content of water.
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What is concentration equation?
Concentration (mg/litre)= mols/litre * molecular weight
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What is the threat to oxygen supply in water?
Oxygen consuming processes reduce concentration to zero of oxygen in water. Oxygen content in water is important as it determines aerobic/anaerobic conditions
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How can we calculate organic matter needed to consume a certain amount of oxygen?
If 30g of CH2O (organic matter) uses up 32g of oxygen, we can determine the weight of CH2O to consume 8.5mg/L of O2. Mass organic (30)/mass oxygen(32) * O2 to be consumed (8.5mg) = 7.9mg/l needed
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What is biochemical oxygen demand?
Fish have dissolved oxygen (DO) requirements. Biochemical oxygen demand is a measure of pollution (higher if more polluted), measures dissolved oxygen consumed as microbes/bacteria break down organic matter
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What is a consequence of high BOD?
High BOD increases will cause oxygen to fall rapidly.
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What is BOD5?
BOD5 - Amount of dissolved oxygen used in water sample by micro-organisms in closed systems as they break down matter in 5 days at 20 degrees
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How can we run a BOD test?
Dead fish occur due to O2 depletion. BOD test: ran for 5 days, temp kept at 20 degrees, bottles kept in dark. Dissolved oxygen measured at start and end. BOD= Dilution factor * (initial DO - final DO) (ie if diluted 1:100 for very strong waste)
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What is sometimes added in the BOD test?
If waste doesn't contain bacteria for the BOD test it's added
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What does the oxygen sag curve show?
A dissolved oxygen distance graph at pollution site shows a sudden DO deficit at the place of pollution, then a sag in dissolved oxygen between decomposition zone and septic zone before DO increases at recovery and clean zone.
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What does BOD show on the oxygen sag graph?
At decomposition zone, BOD rises immediately then tails off with distance
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What zones at a pollution site have what fish?
Decomposition zone has trash fish like carp and leeches, a fish absent septic zone with funghi, worms and anaerobic bacteria, then more trash fish in the recovery zone. The clean zone has fish like trouts and bass.
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Other cards in this set

Card 2

Front

What is a base?

Back

Base produces hydroxide ions in water: NaOH-> Na+ +OH-

Card 3

Front

What is ka?

Back

Preview of the front of card 3

Card 4

Front

What is acid dissociation constant?

Back

Preview of the front of card 4

Card 5

Front

What are buffer solutions?

Back

Preview of the front of card 5
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