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chemical tests, tests for:, flame tests for cations, sodium hydroxide…
chemical tests
gas tests
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oxygen
get a glowing splint by blowing out a lit one from a bunsen burner and add it to a boiling tube with oxygen present
if oxygen is present, the splint should relight completely
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ammonia
insert damp litmus paper to a tube with ammonia, or suspected ammonia present
if ammonia is present, the litmus paper will turn blue and a pungent gas known as ammonia gas will be released
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anion tests
carbonate anions
metal carbonates are identified by adding of a few drops of dilute hydrochloric acid. a colourless gas should be given off as the carbonate ions react with the hydrogen ions
sulfate anions
add a few drops of barium chloride solution which has been prior acidified by dilute nitric acid. a white barium sulphate precipitate forms
halide anions
add dilute nitric acid, followed by aqueous silver nitrate solution to your desired compound. if halides are present, a precipitate will form, although some precipitate may form due to reacting with the nitric acid
water tests
blue hydrated copper sulfate turns into white anhydrous copper sulfate when heated. this reaction is reversible so that it goes blue again when we add water to white anhydrous copper sulfate. we use white anhydrous copper sulfate to test if water is present.
water purity tests
calculate the boiling and melting points, and then use the temperature and the time to determine purity
pure water will have 0 and 100 as the melting and boiling points and on a graph, would be represented by straight lines
water that isn't pure will usually have different boiling and melting points and will be represented by curving or irregular lines
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flame tests for cations
dip a nichrome wire loop into, concentrated hydrochloric acid to clean it and remove any unwanted ions, then put it in a bunsen burner non luminous blue flame. then dip it into the HCl again and then into your desired compound, then into the flame. note the colour the flame turns
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