C5

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C5A - Moles and Molar Mass

THE MOLE - 6.023 X 10 TO THE POWER OF 23

  • WHEN YOU GET PRECISELY THAT NUMBER OF ATOMS OR MOLECULES OF ANY ELEMENT OR COMPOUND, THEY WEIGH EXACTLY THE SAME NUMBER OF GRAMS AS THEIR RELATIVE ATOMIC MASS
  • ONE MOLE OF ATOMS OR MOLECULES OF ANY SUBSTANCE WILL HAVE A MASS IN GRAMS EQUAL TO THE RELATIVE FORMULA MASS FOR THAT SUBSTANCE
  • E.G. CARBON - RELATIVE ATOMIC MASS OF 12 - ONE MOLE WEIGHS 12 G
  • MOLAR MASS - THE MASS OF ONE MOLE - MEASURED IN G/MOL E.G. CARBON HAS MOLAR MASS OF 12G/MOL

NUMBER OF MOLES = MASS (G) OF ELEMENT OR COMPOUND / Mr OF ELEMENT OR COMPOUND

RELATIVE MASSES

  • TOO TINY TO WEIGH - MASSES COMPARED WITH 1/12TH OF THE MASS OF CARBON-12 (ISOTOPE OF C)
  • THE RELATIVE ATOMIC MASS OF AN ELEMENT IS THE AVERAGE MASS OF AN ATOM COMPAIRED TO THE MASS OF 1/12TH OF AN ATOM OF CARBON-12
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C5A - Moles and Molar Mass

CALCULATING MASSES IN REACTIONS USING MOLES

  • E.G. CALCULATE MASS OF ALUMINIUM OXIDE FORMED WHEN 135G OF ALUMINIUM OXIDE IS BURNED IN AIR
    • WRITE OUT BALANCED SYMBOL EQUATION
      • 4Al + 3O2 ---> 2Al2O3
    • CALUCULATE NO. OF MOLES OF GIVEN ELEMENT/COMPOUND FOR GIVEN MASS USING FORMULA
      • MOLES = MASS / Mr = 135 / 27 = 5
    • LOOK AT RATIO OF MOLES IN EQUASION
      • 4 MOLES OF Al REACT TO PRODUCE 2 MOLES OF Al2O3 - HALF NUMBER OF MOLES ARE PRODUCED - 5 MOLES OF Al2 WILL REACT TO PRODUCE 2.5 MOLES OF Al2O3
    • CALCULATE THE MASS OF WORKED OUT NUMBER OF GIVEN SUBSTANCE
      • MASS = MOLES X Mr = 2.5 X 102 = 255G
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C5B - Percentage Composition and Empirical Formula

CALCULATING PERCENTAGE COMPOSITION BY MASS OF COMPOUNDS

  • E.G. 42.9G OF POTASSIUM IN 61.6G OF POTASSIUM HYDROXIDE:
    • USE EXPERIMENTAL DATA TO CALCULATE PERCENTAGE COMPOSITION OF K IN KOH: (42.9 / 61.6) X 100
    • OR USE THIS FORMULA:
  • PERCENTAGE COMPOSITION BY MASS = Ar X NO. OF ATOMS OF ELEMENT / Mr OF WHOLE COMPOUND

EMPIRICAL FORMULAS - SIMPLIST RATIO OF ATOMS IN A COMPOUND

  • LIST ALL ELEMENTS IN COMPOUND
  • UNDERNEATH THEM, WRITE EXPERIMENTAL MASSES OR PERCENTAGES
  • DIVIDE EACH MASS OR PERCENTAGE BY Ar OF PARTICULAR ELEMENT TO FIND NO. OF MOLES
  • ROUND UP NUMBERS TO WHOLE NUMBERS IF NECESSARY AND TURN INTO SIMPLE RATIO BY DIVIDING BY WELL CHOSEN NUMBERS
  • GET RATIO IN SIMPLEST FORM - TELLS YOU EMPIRICAL FORMULA
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C5B - Percentage Composition and Empirical Formula

E.G. FIND EMPIRICAL FORMULA OF IRON OXIDE PRODUCED WHEN 44.8G OF IRON REACTS WITH 19.2 G OXYGEN

  • LIST TWO ELEMENTS:                                             Fe (Ar 56)                                        O (Ar 16)
  • WRITE EXPERIMENTAL MASSES                              44.8                                                 19.2
  • DIVIDE BY Ar OF EACH ELEMENT                      44.8 / 56 = 0.8                                  19.2 / 16 = 1.2
  • MULTIPLY BY 10...                                                       8                                                      12
  • ...DIVIDE BY 4                                                               2                                                       3
  • EMPIRICAL FORMULA = Fe2O3
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C5C - Quantitive Analysis

CONCERNTRATION (G PER DM3) = NUMBER OF MOLES / VOLUME (DM3)

  • THE MORE SOLUTE YOU DISSOLVE IN A GIVEN VOLUME, THE MORE CROWDED THE SOLUTE MOLECULES ARE AND THE MORE CONCENTRATED THE SOLUTION
  • MEASURED IN GRAMS PER DECAMETER CUBED - NEED TO CONVERT UNITS GIVEN IN QUESTION:
    • 1 DM3 (1L) = 1 CM3 / 1000
  • E.G. HOW MANY MOLES OF SODIUM CHLORIDE IN 250CM3 OF 3 M (3 MOLAR) SOLUTION?
    • CONVERT UNITS: 250 / 1000 = 0.25
    • REARRANGE EQUASION: MOLES = CONCERNTRATION X VOLUME = 3 X 0.25 = 0.75 MOLES

CONVERTING MOLES PER DM3 TO GRAMS PER DM3

  • MAY BE ASKED TO ANSWER IN G PER DM3 INSTEAD OF MOLES PER DM3
    • WORK OUT RELATIVE FORMULA MASS FOR SOLUTE
    • CONVERT CONCENTRATION PER MOLES INTO CONCENTRATION PER GRAMS
    • MASS IN GRAMS = MOLES X RELATIVE FORMULA MASS
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C5C - Quantitive Analysis

WORKING OUT DILUTION NEEDED

  • MAY BE GIVEN CONCENTRATED SOLUTION AND ASKED TO DILUTE IT TO MAKE IT WEAKER:
    • WORK OUT RATIO OF TWO CONCENTRATIONS
    • MULTIPLY RATIO BY VOLUME OF SOLUTION YOU WANT TO END UP WITH (TELLS YOU HOW MUCH OF ORIGIONAL ACID NEED TO DILUTE)
    • WORK OUT VOLUME OF WATER NEEDED
  • E.G. PRODUCE 500CM3 OF A 0.1 MOL/DM3 SOLUTION OF KOH IF GIVEN 1 MOL/DM3 SOLUTION AND WATER
    • WORK OUT RATIO - DIVIDE TWO CONCENTRATIONS TO GET NUMBER LESS THAN ONE
      • 0.1 / 1 = 1/10 - 1 TO 10 RATIO - 1 IN 10 DILUTION
    • DIVIDE BY WHAT YOU WANT TO END UP WITH
      • VOLUME OF DILUTE = RATIO X FINAL VOLUME = 1/10 X 500 = 60CM3
    • WORK OUT VOLUME NEEDED
      • VOLUME OF WATER = TOTAL VOLUME - VOLUME OF DILUTE = 500CM3 - 50CM3 = 450CM3
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C5C - Quantitive Analysis

GUIDELINE DAILY AMOUNTS

  • GUIDELINE DAILY AMOUNTS - THE AMOUNTS OF NUTRIENTS A HEALTHY ADULT SHOULD EAT IN A DAY IN A HEALTHY DIET
  • PACKAGING - NUTRITIONAL INFORMATION LABELS - TELL YOU AMOUNTS OF NUTRIENTS IN FOOD - TELL YOU PERCENTAGE OF VARIOUS GDA'S PROCUT WILL SUPPLY
  • AMOUNTS MAY NOT ALWAYS BE AMOUNT EATEN BECAUSE:
    • AMOUNTS GIVEN PER 100G OF FOOD - MAY EAT MORE OR LESS THAN THIS
    • MAY ADD OTHER THINGS E.G. CEREAL EATEN WITH MILK

ESTIMATING MASS OF SALT (SODIUM CHLORIDE) FROM SODIUM CONTENT

  • E.G. BREAD CONTAINS 0.2G OF SODIUM (Ar23) - HOW MUCH SALT (SODIUM CHLORIDE - Mr 58.5)?
    • FIND RATIO OF SODIUM CHLORIDES Mr TO Ar: 58.5 / 23 = 2.543...
    • MULTIPLY BY AMOUNT OF SODIUM: 2.543 X 0.2 = 0.5086 G
  • PROBABLY BE OVERESTIMATE - SODIUM WON'T ALWAYS COME FROM SODIUM CHLORIDE - OTHER COMPOUNDS TOO E.G. SODIUM NITRATE USED AS PRESERVATIVE
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C5D - Titrations

TITRATIONS - ALLOW TO FIND OUT EXACTLY HOW MUCH ACID NEEDED TO NEUTRILISE ALKILI (OR VICE VERSA)

  • EQUIPMENT NEEDED:
    • PIPETTE - MEASURE ONE VOLUME OF SOLUTION
    • PIPETTE FILLER - STOPS INHALATION OF ALKALI
    • CONICAL FLASK - HOLDS MIXTURE
    • INDICATOR - TELLS YOU WHEN MIXTURE PH CHANGES
    • BURETTE - MEASURE VOLUMES - LET YOU ADD SOLUTION DROP BY DROP - KNOW QUANTITY USED
  • USING PIPETTE AND PIPETTE FILLER, ADD KNOWN VOLUME (USUALLY 25CM3) ALKALI TO CONICAL FLASK ALONG WITH TWO/THREE DROPS OF INDICATOR
  • FILL BURETTE WITH ACID BELOW EYE LEVEL TO AVOID GETTING IN EYE 
  • ADD ACID TO ALKALI BIT AT A TIME - SWIRL FLASK REGULARLY - GO ESPECIALLY SLOWLY WHEN END POINT ABOUT TO BE REACHED
  • END POINT - POINT WHERE COLOUR CHANGE HAPPENS - WHERE ACID/ALKILI IS NEUTRELISED
  • RECORD VOLUME USED
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C5D - Titrations

WHY YOU NEED TO GET SEVERAL CONSISTANT READINGS

  • TO INCREASE ACCURACY OF TITRATION - SPOT ANOMALOUS RESULTS
  • FIRST TITRATION - ROUGH TITRATION - GET APPROXIMATE IDEA OF WHERE SOLUTION CHANGES COLOUR
  • NEED TO REPEAT WHOLE THING A FEW TIMES - MAKE SURE GET ROUGHLY SAME RESULTS (WITHIN 0.2CM)

INDICATORS

  • UNIVERSAL INDICATOR - USED TO ESTIMATE PH OF SOLUTION - TURNS VERIETY OF COLOURS - EACH REPRESENTS NARROW RANGE OF PH VALUES
  • MADE OF MIXTURE OF DIFFERENT INDICATORS - COLOUR GRADUALLY CHANGES FROM RED (ACIDIC) TO PURPLE (ALKILINE))
  • NOT USED IN TITRATIONS - YOU NEED TO SEE A SUDDEN COLOUR CHANGE AT THE END POINT
  • NEED A SINGLE INDICATOR E.G. PHENOLPHTHALEIN - TURNS FROM CLEAR TO PINK IN PH'S HIGHER THAN 7
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C5D - Titrations

pH CURVES

(http://www.chemguide.co.uk/physical/acidbaseeqia/sasb2.gif)

  • GRADUAL INCREASE IN PH AS ALKALI IS ADDED TO ACID
  • END POINT - SUDDEN CHANGE (ALMOST VERITCAL LINE) - WHERE PH IS 7 - THIS GRAPH, 25CM3 ADDED
  • VOLUME OF ALKALI NEEDED TO NEUTRILISE SOLUTION HERE IS 25CM3
  • WHEN ADDING ACID TO ALKALI, CURVE WILL BE FLIPPED

(http://www.smart-fertilizer.com/loadedFiles/pH%20curve.JPG)

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C5D - Titrations

CALCULATING CONCENTRATION

  • METHOD:
    • WORK OUT HOW MANY MOLES OF KNOWN SUBSTANCE YOU HAVE (N = C X V)
    • WRITE DOWN BALANCED SYMBOL EQUASION FOR REACTION - WORK OUT HOW MANY MOLES OF UNKNOWN SUBSTANCE YOU MUST HAVE HAD
    • WORK OUT CONCENTRATION OF UNKNOWN STUFF (C = N/V)
  • E.G. 25CM3 SODIUM HYDROXIDE IN FLASK OF CONCENTRATION 0.1 MOL/DM3 - TITRATION TAKES 49CM3 HYDROCHLORIC ACID TO NEUTRILISE - CONCENTRATION OF HYDROCHLORIC ACID?
    • MOLES OF KNOWN SUBSTANCE = 0.1 MOL/DM3 X (25/1000) DM3 = 0.0025 MOLS OF SODIUM HYDROXIDE
    • BALANCED SYMBOL EQUASION = NaOH + HCl ---> NaCl + H2O
    • MOLES OF UNKNOWN SUBSTANCE - USE EQUASION TO WORK OUT THAT, WITH EVERY MOLE OF KNOWN SUBSTANCE, YOU MUST HAVE HAD ABOUT 1 MOLE OF HYDROCHLORIC ACID = 0.0025MOLS NaOH
    • CONCENTRATION = 0.0025 MOL / (49/1000) DM3 = 0.0510 MOL/DM3
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C5E - Gas Volumes

COLLECTION METHODS

  • TWO METHODS - BOTH USE CONICAL FLASKS AS STANDARD APERATUS TO COLLECT GASES - WHAT YOU CONNECT DEPENDS ON WHAT TRYING TO COLLECT:
    • GAS SYRINGE - USED FOR COLLECTING ANY GAS - USUALLY GIVE VOLUME ACCURATE TO NEAREST CM3 - IF REACTION TOO VIGOROUS, PLUNGER CAN BE BLOWN OUT OF END OF SYRINGE
    • (http://everythingmaths.co.za/science/grade-12/07-rate-and-extent-of-reaction/pspictures/3b7a7815d9b52439eea4de3dc5d547e2.png)
    • UPTURNED MEASURING CYLINDER OR BURETTE - USE DELIVERY TUBE TO BUBBLE GAS INTO UPSIDE DOWN MEASURING CYLINDER OR GAS JAR FILLED WITH WATER - NO GOOD FOR COLLECTING THINGS WHICH DISSOLVE IN WATER E.G. AMMONIA, HYDROGEN CHLORIDE - UPTURNED BURETTE IS MORE ACCURATE - MEASURES TO NEAREST 0.1CM3
    • (http://www.bbc.co.uk/schools/gcsebitesize/science/images/triple_science/305_bitesize_gcse_tschemistry_howmuch_collectingagas_464.gif)
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C5E - Gas Volumes

MEASURING MASS OF GAS PRODUCED

  • MEASURE MASS OF GAS PRODUCED BY CARRYING OUT EXPERIMENT ON A MASS BALANCE
  • GAS RELEASED - AMOUNT GONE EASILY MEASURED BY MASS BALANCE
  • MOST ACCURATE OF THREE METHODS - MASS BALANCE VERY ACCURATE
  • DISADVANTAGE - RELEASES GAS SRAIGHT INTO ROOM

ONE MOLE OF ANY GAS ALWAYS OCCUPIES 24DM3 AT ROOM TEMPERATURE AND PRESSURE (RTP - 25 DEGREES AND ONE ATMOSPHERES)

STOPPING OF REACTIONS - WHEN ONE REACTANT IS USED UP

  • REACTION STOPS WHEN ALL REACTANT IS USED UP - ANY OTHER REACTANTS ARE EXCESS
  • LIMITING REACTANT - REACTANT USED UP
  • AMOUNT OF PRODUCT FORMED DIRECTLY PROPORTIONAL TO LIMITING REACTANT - E.G. IF LIMITING REACTANT DOUBLED, YEILD WILL DOUBLE
  • REASON - IF YOU ADD MORE REACTANT THERE WILL BE MORE REACTANT PARTICLES TO TAKE PART IN REACTION - MORE PRODUCT PARTICLES
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C5E - Gas Volumes

READING GRAPHS AND TABLES OF REACTIONS

(http://2.bp.blogspot.com/-NSZ9zCVWYYs/UWmNflkRrCI/AAAAAAAAABU/THmz-XWOoY4/s1600/Gradient+of+Graph_Volume+of+gas+evolved.jpg)

  • GRAPH GOES FLAT - Y AXIS - TOTAL VOLUME OF GAS PRODUCED 
    • X AXIS - TOTAL TIME OF REACTION
  • STEEPER CURVE - REACTION FAST
  • CURVE STARTS GETTING LESS STEEP - REACTION SLOWING DOWN - GETTING READY TO STOP
  • MORE THAN ONE CURVE ON GRAPH:
    • STEEPEST CURVE WILL BE QUICKEST REACTION
    • CURVE THAT GOES HORIZONTAL AT HIGHEST POINT PRODUCES MOST PRODUCT - LEAST AMOUNT OF LIMITING REACTANT
    • ALL CURVES GO FLAT AT SAME HEIGHT - SAME AMOUNT OF LIMITING REACTANTS
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C5F - Equilibrium

REVERSABLE REACTIONS - REACTIONS WHERE THE PRODUCTS OF THE REACTION CAN THEMSELVES REACT TO                                                    GIVE THE ORIGIONAL REACTANTS - A + B <---> C + D

REACHING EQUILIBRIUM - FORWARD REACTION IS GOING AT EXACT SAME RATE AS BACKWARD REACTION

  • AS REACTANTS A AND B REACT, THEIR CONCENTRATIONS FALL - FORWARD REACTION WILL SLOW DOWN
  • AS MORE AND MORE PRODUCTS (C AND D) ARE FORMED, THEIR CONCENTRATIONS WILL RISE - BACKWARD REACTION WILL SPEED UP
  • AFTER WHILE, FORWARD AND BACKWARD REACTION WILL BE GOING AT SAME RATE - EQUILIBRIUM REACHED
  • BOTH REACTIONS STILL HAPPENING BUT THERE IS NO OVERALL EFFECT - CONCENTRATIONS OF REACTANTS AND PRODUCTS WILL HAVE REACHED A BALANCE AND WON'T CHANGE
  • ONLY REACHED IF REVERSABLE REACTION TAKES PLACED IN A CLOSED SYSTEM - NONE OF REACTANTS OR PRODUCTS CAN ESCAPE

POSITION OF EQUILIBRIUM

  • EQUILIBRIUM LIES TO RIGHT - CONCENTRATION OF PRODUCT GREATER THAN CONCENTRATION OF REACTANT
  • EQUILIBRIUM LIES TO LEFT - CONCENTRATION OF REACTANT GREATER THAN CONCENTRATION OF PRODUCT
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C5F - Equilibrium

FACTORS WHICH CHANGE POSITION OF EQUILIBRIUM

  • TEMPERATURE 
  • PRESSURE (ONLY EFFECTS GASES)
  • CONCENTRATION

ADDING A CATALYST DOES NOT CHANGE EQUILIBRIUM POSITION - SPEED UP FORWARD AND BACKWARDS REACTION BY THE SAME AMOUNT - REACTION REACHES EQ. QUICKER BUT SAME AMOUNT PRODUCT FORMED

EQUILIBRIUM COUNTERACTS ANY CHANGE MADE

  • TEMPERATURE - ALL REACTIONS ARE EXOTHERMIC IN ONE DIRECTION AND ENDOTHERMIC IN ANOTHER
    • TEMP DECREASED - EQUILIBRIUM MOVE TO INCREASE IT - EQUILIBRIUM MOVES IN ENDOTHERMIC DIRECTION TO PRODUCE MORE HEAT
    • RAISE TEMPERATURE - EQUILIBRIUM MOVE IN ENDOTHERMIC DIRECTION TO DECREASE IT
  • PRESSURE - ONLY AFFECTS EQUILIBRIUM INVOLVING GASES
    • PRESSURE INCREASED - EQUILIBRIUM MOVES IN DIRECTION WHERE FEWER MOLES OF GAS
    • PRESSURE DECREASED - EQUILIBRIUM MOVES IN DIRECTION WHERE MORE MOLES OF GAS
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C5F - Equilibrium

  • CONCENTRATION - 
    • INCREASE CONCENTRATION OF REACTANTS - EQUILIBRIUM DECREASES IT BY SHIFTING TO THE RIGHT (MAKE MORE PRODUCT)
    • INCREASE CONCENTRATION OF PRODUCT - EQUILIBRIUM MOVES TO LEFT - MAKES MORE REACTANTS

EQUILIBRIUM TABLES AND GRAPHS

  • AS PRESSURE INCREASES, PROPORTION OF AMMONIA INCREASES - INCREASED PRESSURE SHIFTS EQUILIBRIUM TO SIDE WITH FEWER MOLES OF GAS
  • MULTIPLE LINES ON GRAPHS:
    • EACH LINE REPRESENTS A DIFFERENT TEMP
    • TEMP INCREASES - PROPORTION OF AMMONIA DECREASES (BACKWARDS REACTION ENDOTHERMIC - EQUILIBRIUM TRYING TO CHANGE TO REDUCE TEMP)
    • CONDITIONS WHICH GIVE MOST PRODUCT - HIGHEST CURVE ON GRAPH
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C5F - Equilibrium

THE CONTACT PROCESS - THREE STAGES:

  • FIRST STAGE - BURN SULFUR IN AIR TO MAKE SULFUR DIOXIDE - S (s) + O2 (g) ---> SO2 (g)
  • SECOND STAGE - SULPHUR DIOXIDE OXIDISED WITH CATALYST TO MAKE SULPHUR TRIOXIDE
    • 2SO2 (g) + O2 (g) <---> 2SO2 (g)
  • SULFUR TRIOXIDE USED TO MAKE SULPHURIC ACID - SO2 (g) + H2O (l) ---> H2SO4 (aq)

CONDITIONS USED FOR SECOND STAGE 

  • 2SO2 +O2 <---> 2SO3 - REVERSABLE REACTION
  • TEMPERATURE - MAKING SULPHUR TRIOXIDE IS AN EXOTHERMIC REACTION
    • TEMP NEEDS TO BE REDUCED TO SHIFT EQUILIBRIUM TO RIGHT TO GET MORE PRODUCT
    • REDUCING TEMP SLOWS REACTION - COMPROMISE TEMP OF 450 DEGREES USED - YEILD AND SPEED
  • PRESSURE - TWO MOLES OF PRODUCT COMPARED TO 3 MOLES OF REACTANT
    • MORE  PRODUCT - PRESSURE INCREASED - EQUIIBRIUM SHIFTS TO RIGHT TO REDUCE PRESSURE
    • INCREASING PRESSURE EXPENSIVE - NOT NECESSARY - EQUILIBRIUM ALREADY ON RIGHT
    • ATMOSPHERIC PRESSURE (1 ATMS) USED
  • CALTALYST - VANADIUM PETOXIDE (V2O5) - INCREASE RATE OF REACTION - DOESN'T AFFECT EQUI. POSITION 
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C5G - Strong and Weak Acids

ACIDS - STRONG OR WEAK?

  • ACIDS IONISE IN WATER - PRODUCE H+ IONS - E.G. HNO3 ---> H+ + NO3-
    • STRONG - IONISE COMPLETELY IN WATER - LOTS OF H+ RELEASED E.G. HYDROCHLORIC, SULPHURIC
    • WEAK - DON'T FULLY IONISE - SMALL NUMBERS OF H+ RELEASED E.G. ETHANOIC, CITRIC, CARBONIC
  • IONISATION OF WEAK ACID - REVERSABLE REACTION - SETS UP EQUILIBRIUM MIXTURE - ONLY FEW H+ IONS RELEASED - EQUILIBRIUM LIES TO LEFT
  • PH - MEASURE OF CONCENTRATION OF H+ IONS IN SOLUTION - STRONG HAVE PH 1 OR 2 ETC.
  • EXAMPLES OF STRONG AND WEAK ACIDS:
    • STRONG - HCl ---> H+ + Cl-
    • WEAK - CH3COOH <---> H+ + CH3COO-

CONCENTRATION AND STRENGTH

  • STRENGTH - DESCRIBES PROPORTION OF ACID MOLECULES IONISE IN WATER
  • CONCENTRATION - MEASURES HOW MANY MOLES OF ACID THERE ARE IN A DM3 OF WATER - HOW WATERED
    • DESCRIBES TOTAL NUMBER OF DISSOLVED ACID MOLECULES - NOT NUMBER THAT PRODUCE H IONS
    • MORE ACID MOLECULES PER DM3 = MORE CONCENTRATED - CAN HAVE CONCENTRATED WEAK ACID
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C5G - Strong and Weak Acids

REACTION RATES

  • HYDROCHLORIC ACID (STRONG) AND ETHENOIC ACID (WEAK) BOTH REACT WITH Mg TO GIVE HYROGEN
    • 2HCl + Mg ---> MgCl2 + H2
    • 2CH3COOH + Mg ---> Mg(CH3COO)2 + H2
  • HYDROCHLORIC ACID AND ETHANNOIC ACID REACT WITH CALCIUM CARBONATE TO GIVE CO2
    • 2HCL + 2CaCO3 ---> CaCl2 + H2O + CO2
    • 2CH3COOH + CaCO3 ---> Ca(CH3COO)2 + H2O + CO2
  • DIFFERENCE - RATE OF REACTION - HCL REACTS FASTER THAN ETHANOIC OF SAME CONCENTRATION  - HCL STRONG ACID AND ETHANOIC WEAK
  • WHEN WEAK ACID PUT INTO WATER, RELEASES FEW H+ IONS - CONCENTRATION OF H+ IONS LOW COMPARED TO STRONG ACID - WHEN MAGNESIUM ADDED, COLLISION FREQUENCY LOWER
  • H+ IONS REACT - CONCENTRATION OF H+ DECREASES - EQUILIBRIUM SHIFTS TO COMPENSATE - MORE H+ IONS RELEASED - THESE IONS REACT - EQUILIBRIUM SHFTS AND SO ON - AS IONS REMOVED, MORE SUPPLIED
  • DIFFERENT TO STRONG ACID - ALL PARTICLES IONISED - LOADS OF H+ IONS RELEASED - WHEN MG ADDED, COLLISION FREQUENCY HIGH                                                                                                                                                                                                                                                                                                                                     
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C5G - Strong and Weak Acids

GAS VOLUMES

  • HYDROCHLORIC ACID WILL REACT FASTER THAN ETHANOIC BUT AMOUNT OF YEILD WILL BE THE SAME
  • IF CONCENTRATIONS SAME, NUMBER OF MOLECULES IN A LITRE OF WATER WILL BE SAME
  • EACH OF THESE MOLECULES CAN LET GO OF ONE HYDROGEN ION
    • HCL ---> H+ + CL-
    • CH3COOH <---> H+ + CH3COO-
  • HYDROCHLORIC ACID HAS LET GO OF THEM ALL AT ONCE, RATHER THAN GRADUALLY 
  • SINCE TOTAL NUMBER OF H+ IONS AVAILABLE IS SAME, VOLUME OF GASEOUS PRODUCTS SAME

CONDUCTIVITY

  • ETHANOIC ACID - LOWER ELECTRICAL CONDUCTIVITY THAN SAME CONCENTRATION OF HYDROCHLORIC
  • IONS CARRY CHARGE THROUGH ACID SOLUTIONS AS THEY MOVE - LOWER CONCENTRATION OF IONS MEANS LESS CHARGE CAN BE CARRIED
  • ELECTROLYSIS OF HCL AND ETHANOIC - PRODUCES H2 - BOTH PRODUCE H+ IONS
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C5H - Ionic Equations and Precipitation

PRECIPITATION REACTIONS - TWO SOLUTIONS REACTING TOGETHER TO MAKE AN INSOLUBLE SUBSTANCE

  • PRECIPITATE - INSOLUBLE SUBSTANCE FORMED FROM PRECIPITATION REACTION - MAKES SOLUTION CLOUDY
  • MOST PRECIPITATION REACTIONS IONS - HAVE TO BE ABLE TO MOVE - COLLIDE WITH EACHOTHER AND REACT - IONIC SUBSTANCES HAVE TO BE IN SOLUTION OR MOLTEN TO REACT
  • USUALLY EXTREMELY QUICK - HIGH COLLISION FREQUENCY BETWEEN IONS

IONIC EQUATIONS

  • BARIUM CHLORIDE + SODIUM SULPHATE ---> BARIUM SULPHATE + SODIUM CHLORIDE
  •         BaCl2 (aq)          +         NaSO4 (aq)        --->     BaSO4 (s)               +      2NaCl (aq)
  • PRECIPITATION REACTION - START WITH TWO SOLUTIONS AND END UP WITH SOLID
  • BARIUM AND SULPHATE IONS FORM PRECIPITATE
  • SPECTATOR IONS - IONS THAT DON'T CHANGE DURING REACTION
  • SODIUM AND CHLORIDE IONS - DISSOLVED IN SOLUTION BEFORE REACTION- STILL DISSOLVED AFTERWARDS - SPECTATOR IONS
  • IONIC EQUATION - CONCENTRATES ON PARTS OF REACTION THAT RACTS - IGNORES SPECTATOR IONS
  • Ba 2+ (aq) + SO4 2- (aq) ---> BaSO4 (s) 
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C5H - Ionic Equations and Precipitation

TESTING FOR SULFATE IONS (SO4 2-)

  • ADD DILUTE HYDROCHLORIC ACID FOLLOWED BY BARIUM CHLORIDE
  • WHITE PRECIPITATE OF BARIUM SULPHATE - MEANS ORIGIONAL COMPOUND WAS SULFATE
  • E.G. ADDING HCL TO BARIUM CHLORIDE AND POTASSIUM SULFATE PRODUCES WHITE PRECIPITATE

TESTING FOR CHLORIDE (Cl-), BROMIDE (Br-) AND IODIDE (I-) IONS

  • ADD DILUTE NITRIC ACID FOLLOWED BY LEAD NITRATE
    • CHLORIDE GIVES WHITE PRECIPITATE                                               Pb 2+ (aq) + 2Cl- (aq) ---> PbCl2 (s)
    • BROMIDE GIVES CREAM PRECIPITATE                                               Pb 2+ (aq) + 2Br- (aq) ---> PbBr2 (s)
    • IODIDE GIVES YELLOW PRECIPITATE                                                  Pb 2+ (aq) + 2I- (aq) ---> PbI2 (s)

PICKING REACTANTS AND SPECTATOR IONS

  • TO MAKE INSOLUBLE SALT, IONS NEEDED - E.G. LEAD IODIDE NEEDS LEAD AND IODINE IONS - NEED TO BE IN SOLUTION TO MOVE AROUND
  • NITRATES SOLUBLE - GET LEAD FROM LEAD NITRATE SOLUTION AND IODINE FROM POTASSIUM IODIDE
  • Pb(NO3)2 (aq) + 2KI (aq) ---> PbI2 (s) + 2KNO3 (aq)                                    Pb 2+ (aq) + 2I- (aq) --> PbI2 (s)
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C5H - Ionic Equations and Precipitation

PREPARING INSOLUBLE SALTS - METHOD

  • STEP ONE - MIX SOLUTIONS OF REACTANTS
    • ADD 1 SPATULA OF LEAD NITRATE TO TEST TUBE, FILL WOTH DISTILLED WATER
    • SHAKE THOROUGHLY TO ENSURE LEAD NITRATE DISSOLVED
    • DO THE SAME WITH ONE SPATULA OF POTASSIUM IODIDE
    • TIP TWO SOLUTIONS INTO BEAKER, STIR AND SEE SALT PRECIPITATE OUT
  • STEP TWO - FILTERATION
    • PUT FOLDED FILTER PAPER INTO FILTER FUNNEL - STICK FUNNEL INTO CONICAL FLASK
    • POUR CONTENTS OF BEAKER INTO MIDDLE OF FILTER PAPER, MAKING SURE NONE SPILLS DOWN SIDES OF FILTER PAPER SO SOLIDES DONT GET THROUGH
    • SWILL OUT BEAKER WITH MORE DISTILLED WATER - MAKE SURE ALL PRODUCT GOT FROM BEAKER
  • STEP THREE - WASH AND DRY RESIDUE
    • RINSE FILTER PAPER WITH DISTILLED WATER - MAKE SURE ALL SOLUBLE SALTS WASHED AWAY
    • SCRAPE LEAD IODIDE ONTO FRESH FILTER PAPER AND LEAVE TO DRY
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