Flashcards
Chem C8 - F
Flashcards do conjunto (93)
- 1What is a pure substance?a single element or compound,
not mixed with any other substance
-it's in its natural state
(nothing has been added) - 22 examples of a pure substance-Pure milk
-Beeswax - 3What tells you how pure a substance is?-measure boiling or melting point and compare it with that of the pure substance (can find from a data book)
~distinguishes pure substances from mixtures - 4A chemically pure substance will ____ or ____ at a ______ ___________-melt
-boil
-specific temperature - 5The closer your measure value is to the actual melting or boiling point, the...purer your sample is
- 6What will impurities in your sample do?-they will lower the melting point and increase the melting range of your substance
-will also increase the BP and may result in your sample boiling at a range of temperatures - 7What are formulations?they're useful mixtures with each chemical having a precise purpose (mixtures with the exact measured quantities of components)
- 8Why do formulations have the components mixed in ________ _______ carefully?-measured quantities
~to ensure that the product has the required properties - 9Give 7 examples of formulations-fuels
-cleaning agents
-paints
-medicines
- (metal) alloys
-fertilisers
-foods
-cosmetics - 10E.g. Paints are formulations composed of: Pigmentgives the paint colour
e.g. titanium oxide is used as a pigment in white paints) - 11E.g. Paints are formulations composed of: Solventused to dissolve the other components and alter the viscosity (runniness)
- 12E.g. Paints are formulations composed of: Binder (resin)forms a film that holds the pigment in place after it's been painted on
- 13E.g. Paints are formulations composed of: Additivesadded to further change the physical and chemical properties of the paint.
~ depending on the purpose of the paint, the chemicals used and their amounts will be changed so the paint produced is right for the job - 14Where are formulations important?-In the pharmaceutical industry
e.g. by altering the formulation of a pill, chemists can make sure it delivers the drug to the correct part of the body at the right concentration, that it's consumable and has a long shelf life - 15How can you choose a formulation with the right composition for your particular use in a product?-it has information about its composition on the packaging
E.g. the ratio or percentage of each component - this tells you a product's formulation - 16What is chromatography?an analytical method used to separate the substances in a mixture
~ you can then use it to identify the substance - 17How many phases does chromatography have?2
- 18Explain the "mobile phase"-where the molecules can move
-this is always a LIQUID or GAS - 19Explain the "stationary phase"-where the molecules can't move
-can be a SOLID or a really THICK LIQUID - 20During a chromatography experiment, the substances in the sample constantly ____ between the _____ and _________ phases What is formed between the 2 phases?-move
-mobile
-stationary
~ an equilibrium is formed - 21What does separation depend on?the distribution of substances between the phases ---- whether it spends more time in the mobile phase or the stationary phase
- 22The chemicals that spend more time in the mobile phase than the secondary phase will...move further through the secondary phase
- 23What will components in a mixture normally do through the secondary phase?separate
- 24What do the separated components form?spots
~ the number of spots formed may change in different solvents as the distribution of the chemical will change depending on the solvent - 25A pure substance will only ever form...-one spot in any solvent
~since there is only one substance in the sample - 26In paper chromatography what is the stationary phase?the chromatography paper
(often filter paper) - 27In paper chromatography what is the mobile phase?the solvent
(e.g. ethanol or water) - 28What 2 factors does the amount of time the molecules spend in each phase depend on?1) how soluble they are in the solvent
2) how attracted they are to the paper - 29Molecules with a _____ _________ in the solvent, and which are ___ _______ to the paper, will spend more time in the ______ _____ and they'll be carried ___________- higher solubility
- less attracted
- mobile phase
- further up the paper - 30What is the result of chromatography analysis called?a chromatogram
- 31What is an Rf value?the ratio between the distance travelled by the dissolved substance (the solute) and the distance travelled by the solvent
- 32Equation to calculate Rf value
- 33What can be used to help identify the compounds?Different compounds have different Rf values in different solvents, which can be used to help identify the compounds
- 34The compounds in a mixture may separate into ________ spots depending on the _______ but a pure compound will produce a single ___ in all solvents-different
-solvent
-spot - 35Chromatography diagram
- 36What is the Rf value of a substance dependant on?the solvent you use
-if you change the solvent the Rf value will change - 37You can test both the _______ and the _______ in a number of different solvents-mixture
-reference - 38What might the compounds in a mixture separate into?different spots depending on the solvent
- 39What will a pure compound produce?a single spot in ALL solvents
- 40Chromatogram diagram
- 41If the Rf value of the reference matches the Rf value of one of the spots in the mixture in all the solvents, then it's likely the...reference compound is present in the mixture
- 42If the spot in the mixtre and the spot in the reference only have the same Rf value in ____ of the ______, then...-some
-solvents
the reference isn't present in the fixture - 43Test for chlorine
- 44Test for oxygen
- 45Test for carbon dioxide
- 46Test for hydrogen
- 47What do flame tests identify?metal ions (cations)
- 48Flame test: Lithium ions
- 49Flame test: Sodium ions
- 50Flame test: Potassium ions
- 51Flame test: Calcium ions
- 52Flame test: Copper ions
- 53What do you require to do the flame test?-clean a platinum wire loop by dipping it in some dilute HCI and then holding it in a blue flame from a Bunsen burner until it burns without any colour
-then dip the loop into the sample you want to test and put it back in the flame
-record the colour of the flame - 54If a sample containing a mixture of ions is used some flame colours can be...masked
- 55What can you use these colours for? However, it only works for samples that contain a...-to detect and identify different ions
-single metal ion
~ If the sample tested contains a mixture of metal ions, the flame colours of some ions may be hidden by the colours of others - 56Many metal hydroxides are...insoluble and precipitate out of solution when formed
~ Some of these hydroxides have a characteristic colour. So in this test, you add a few drops of sodium hydroxide solution to a solution of your mystery compound -- all in the hope of forming an insoluble hydroxide - 57If you get a coloured insoluble hydroxide...you can often tell which metal was in the compound
- 58Colour of precipitate: Calcium, Ca²+White
- 59Ionic equation for precipitate formation: Calcium, Ca²+
- 60Colour of precipitate: Copper(ll), Cu²+Blue
- 61Ionic equation for precipitate formation: Copper(ll), Cu²+
- 62Colour of precipitate: Iron(ll), Fe²+Green
- 63Ionic equation for precipitate formation: Iron(ll), Fe²+
- 64Colour of precipitate: Iron(lll), Fe³+Brown
- 65Ionic equation for precipitate formation: Iron(lll), Fe³+
- 66Colour of precipitate: Aluminium, Al³+White at first. But then redissolves in excess NaOH to form a colourless solution
- 67Ionic equation for precipitate formation: Aluminium, Al³+(don't need to know the equation for how the aluminium hydroxide precipitate dissolves)
- 68Colour of precipitate: Magnesium, Mg²+White
- 69Ionic equation for precipitate formation: Magnesium, Mg²+
- 70Which 3 solutions form coloured precipitates?copper(ll), iron(ll) and iron(lll)
- 71Carbonates are substances that contain...
- 72What can help detect carbonates?dilute acid
- 73What do carbonates react with and what do they form?-react with dilute acids
-form carbon dioxide gas - 74What can carbon dioxide be identified with?limewater
- 75How can you test whether a mystery solution contains carbonate ions or not?by putting a sample in a test tube and then using a dropping pipette to add a couple of drops of dilute acid. Then connect the test tube to the limewater. If carbonate ions are present, carbon dioxide will be released that will turn the limewater cloudy when it bubbles through it.
- 76What is the equation for the carbon dioxide gas test?
- 77Test for sulfates with...HCI and Barium Chloride
- 78To identify sulfate ions (SO₄²-)use a dropping pipette to add a couple of drops of dilute hydrochloric acid (HCI) followed by a couple drops of barium chloride solution (BaCl₂) to a test tube containing your mystery solution.
- 79Why is HCI added?To get rid of any traces of carbonate ions before you do the test.
These would also produce a precipitate, so they'd confuse the results. - 80If sulfate ions are present, what will form?a white precipitate of barium precipitate
- 81What is the equation for present sulfate ions?
- 82Test for halides (Cl-, Br-, I-) with...nitric acid and silver nitrate
- 83To identify a halide ion:add a couple drops of dilute nitric acid (HNO₃), followed by a couple drops of silver nitrate solution), AgNO₃, to your mystery solution
- 84—
- 85—
- 86—
- 87What happens during flame emission spectroscopy?-a sample is placed in a flame
-as ions heat up their electrons become excited
-when the electrons drop back to their original energy levels, they transfer energy as light
--- the light passes through a spectroscope, which can detect different wavelengths of light to produce a line spectrum - 88What does the combination of wavelengths emitted by an ion depend on?-its charge & its electron arrangement
~since no 2 ions have the same change and the same electron arrangement, different ions emit different wavelengths of light.
~so each ion produces a different pattern of wavelengths, and has a different line spectrum - 89What does the intensity of the spectrum indicate?-the concentration of that ion in solution
~this means that line spectrums can be used to identify the (metal) ions in solution and calculate their concentrations - 90Flame spectroscopy can also be used to identify different ions in...mixtures
~this makes it more useful than flame tests, which only work for substances that contain a single metal ion - 91What can machines analyse?Unknown substances
- 92What can be detected and identified using instrumental methods?elements and compounds
- 93Give 3 advantages of using instrumental methods (machines)1) Very sensitive - can detect even the tiniest amounts of substances
2) Very fast - and tests can be automated
3) Very accurate
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- Year 10 Chemistry FlashCards sobre Chem C8 - F, criado por malaika khan em 05-03-2020.
- Criado por
- malaika khan
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