Topic 1 - Qualitative Analysis Flashcards
Why is chemical analysis useful?
Blood tests can monitor general health, diagnose diseases, and check to see the alcohol content of someones blood. Water companies use it to check the purity of the drinking water by analysing for potentially dangerous chemicals.
What is qualitative analysis?
It tells you what substance is present. It is used to detect poisonous substances in things like drinking water.
What is quantitative analysis?
This tells you how much of a substance is present. It would be used in circumstances such as testing the amount of alcohol a driver has consumed.
How do you test for positive metal ions using flame tests?
Clean a nichrome wire by dipping in HCL then heating in a bunsen flame. Place the sample on the clean wire and place in a blue bunsen flame.
What colours are created in flame tests?
Na, K, Ca, Cu
Sodium (Na+) - Yellow
Potassium (K+) - Lilac
Calcium (Ca2+) - Brick red
Copper (Cu2+) - Blue/green
How do you test for positive metal ions using sodium hydroxide?
Dilute sodium hydroxide solution is added to a suspected ion. Colour of precipitate is noted.
What colours are the precipitates created?
Al, Ca, Cu, Fe2, Fe3
Aluminium (Al3+) - White precipitate, dissolves in excess NaOH
Calcium (Ca2+) - White precipitate
Copper (Cu2+) - light blue precipitate
Iron II (Fe2+) - Dark green ppt
Iron III (Fe3+) - Brown ppt
what is the ionic equation for aluminium reacting with sodium hydroxide?
Al3+(aq) + 3OH-(aq) -> Al(OH)3(s)
How do you test for acids (containg H+)
Blue litmus paper - goes red
Universal indicator - goes red, yellow, or orange depending on strenght of acid
How do you test for ammonium ions (NH4+)?
Add NaOH solution and warm. Test any gas given off with red litmus paper. It will turn blue
What is the ionic equation of ammonium reacting with sodium hydroxide
NH4+(aq) + OH-(aq) -> NH3(g) + H2O(l)
How do you test for carbonate ions (CO32-)?
Add dilute hydrochoric acid, then bubble the gas produced through limewater. Fizzing and a colourless gas that turns limewater cloudy.
what is the equation of a carbonate reacting with HCL
CO32-(aq) + 2H+(aq) -> H2O (l) + CO2(g)
How do you test for hydroxide ions (OH-) found in alkalis.
red litmus paper turns blue
universal indicator turns dark green, violet, or dark blue depending on the strength of the alkali.
How do you test for sulphate ions (SO42-)?
Add dilute hydrochloric acid, then a few drops of barium chloride solution (BaCl2). White ppt of barium sulphate is formed.
