Chapter 8, 9, 10, 11 Flashcards by Dania El-Ghattis

what color does litmus turn for acidic & alkaline solutions?

acidic = red
alkaline = blue

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what color does phenolphthalein turn for acidic & alkaline solutions?

acidic = colourless
alkaline = pink

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what color does methyl orange turn for acidic & alkaline solutions?

acidic = red
alkaline = yellow

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strong vs concentrated

strong = completely dissociated into ions
concentrated = high number of moles of solute per litre of solution

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meaning of corrosive

chemically reactive

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weak acids

ethanoic acid (CH3COOH)
carbonic acid (H2CO3)
phosphoric acid (H3PO4)
sulfurOUS acid (H2SO3)
nitrOUS acid (HNO2)

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strong acids

HCl
nitrIC acid (HNO3)
sulfurIC acid (H2SO4)
HBr
HI
perchloric acid (HClO4)
chloric acid (HClO3)

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What is the H+ concentration of 0.0100 M H2SO4?

0.0100 x 2 = 0.0200 M

remember to use this ^ value for pH calculations

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examples of neutralisation reactions?

acid & metal hydroxide
acid & metal oxide
acid & base
acid & metal carbonate
acid & metal hydrogen carbonate

NOTTTTT ACID & METAL NO

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examples of neutralisation reactions?

acid & metal hydroxide
acid & metal oxide
acid & base
acid & metal carbonate
acid & metal hydrogen carbonate

NOTTTTT ACID & METAL NO

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outline one application of oxidising agents

can be used as disinfectants

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why is the use of chlorine as a disinfectant of concern?

due to its ability to oxidise other species forming harmful by-products (e.g. trichloromethane)

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where does oxidation occur for BOTH voltaic & electrolytic cells?

at the ANODE

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where does reduction occur for BOTH voltaic & electrolytic cells?

at the CATHODE

RUKAYA ATE COOKED AARDVARKS

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distinguish b/w voltaic & electrolytic cells

VOLTAIC (galvanic) = SPONTANEOUS, convert chemical energy –> electrical energy
CPRANO

ELECTROLYTIC = NON-SPONTANEOUS, convert electrical energy –> chemical energy
PANCake

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How is a redox reaction used to produce electricity in a voltaic cell?

e.g. zinc half cell connected to copper half cell
zinc is higher in activity series than copper so electrons will flow from zinc half cell to copper half cell
zinc electrode eventually gets smaller (as solid zinc goes into solution as Zn2+)
Cu electrode gradually gets larger as it becomes coated w/ copper (Cu2+ ions in sol pick up the electrons to form solid Cu)
COLOUR OF SOLUTION IN CU HALF CELL BECOMES PALER AS COPPER IONS BECOME COPPER ATOMS

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what does voltage produced depend on (voltaic cell)?

depends on relative difference b/w the 2 metals in the activity series
greater distance on activity series = higher voltage

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function of salt bridge

completes the circuit & keeps the half cells electrically neutral
negative ions go into Zn half cell
positive ions go into Cu half cell

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consequences of NO salt bridge

buildup of Zn2+ ions in left beaker –> solution becomes positive overall, no more oxidation of Zn to Zn2+
decrease in Cu2+ concentration in right beaker –> solution would have negative charge & further reduction of Cu2+ ions would be opposed

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which metal will be the negative electrode in the voltaic cell (anode)?

the more reactive metal will have the greater tendency to be oxidised & will be the anode

what does the single vertical line represent?

phase boundary (b/w solid & aq sol)

what does the double line represent?

the salt bridge

define electrolysis

the breaking down of a substance (in molten state or solution) by the passage of electricity through it

why electrodes usually made of graphite?

it is a fairly inert non-metal which conducts electricity

define electrolyte

a solution or molten compound that will conduct electricity, with decomposition at the electrodes as it does so contains IONS that are free to move towards the electrodes

How do electrolytic cells carry an electric current?

- battery provides source of electrical energy - pushes electrons onto the cathode, making it negatively charged - electrons are drawn OUT of the anode, making it positively charged - at the anode, oxidation occurs, releasing electrons that are then attracted to the positively charged anode - at the cathode, reduction occurs, which uses up the electrons that are building up on the cathode

one application of electrolysis

used to obtain reactive metals, such as sodium, from their common ores

Define BOD

the amount of oxygen used by aerobic microorganisms in water to decompose the organic matter in water over a fixed period of time (~5 days) at a fixed temperature (~20C)

BOD levels

1-3 very good 3-5 moderately clean 6-9 poor (some microorganisms present) 100+ very polluted

What is the oxidation state of sulfur in (S4O6)2- ?

+2.5

What are random uncertainties caused by?

caused by limitations of the measuring apparatus & other uncontrollable variables that are inevitable in any experiment

What are random uncertainties caused by?

caused by limitations of the measuring apparatus & other uncontrollable variables that are inevitable in any experiment

how can effects of random uncertainties be limited?

- conducting repeat trials / measurements - careful design of experiment - can never be completely eliminated

uncertainties are usually quoted to how many sig figs? for analog instruments

usually 1 sig figs only remember: half the smallest division to which you take a reading

e.g. of human limitation

reaction time

define precision

a measure of how close a series of measurements are to one another

define accuracy

how close a measurement is to the actual value of a particular quantity

what causes systematic errors?

occur as a result of a flaw in the experimental design or apparatus cannot be reduced by conducting repeat trials

equation for percentage error

percentage error = (experimental value - theoretical value) / theoretical value x 100 If the experimental value is less than the theoretical value, the percentage error will be negative & vice versa

equation for percentage uncertainty (%)

(absolute uncertainty / measurement) x 100%

how to calculate uncertainty of the mean?

take the uncertainty of the mean to be 2/3 of the deviation from the mean

when quantities w/ uncertainties are added or subtracted. . .

the ABSOLUTE uncertainties are ADDED

when quantities w/ uncertainties are multiplied or divided. . .

the PERCENTAGE uncertainties should be ADDED

if 12.12 +/- 0.01 is multiplies by 3, what is the answer?

36.36 +/- 0.03 for division, u divide the uncertainty by 3 as well

how to work out gradient of curve at specific point

draw a tangent to the curve at the desired point work out the gradient of the tangent as usual

IHD is. . .

the number of double bond equivalents

formula for IHD

2x+2-y / 2

what is the IHD of benzene?

4, because it has 1 ring and the equivalent of 3 double bonds

rules for IHD

1. ignore O 2. count a halogen as a hydrogen 3. if it has nitrogen atoms, subtract 1 hydrogen atom for every nitrogen atom, & then calculate as normal