Quantitative analysis Flashcards
how is hard water formed
water in rivers, lakes and reservoirs may flow over rocks containing calcium or magnesium ions. e.g. calcium carbonate is the main compound in the limestone and chalk found in some parts of the country. some of the calcium or magnesium ions dissolve in the water, forming hard water.
what is avagadros number
(6.02*10^23). is the number of carbon atoms in 12g of carbon
how can soluble salts be made
1) using an acid and an excess of an insoluble base, such as copper oxide. 2) using an acid and an exact amount of a soluble base, such as sodium hydroxide solution.
Describe how to carry out simple acid-base titrations using burette, pipette and suitable acid-base indicators
use a pipette to transfer a known volume of alkali to a conical flask. add a few drops of phenolphalein indicator. fill the burette with acid and note the reading. open the tap and add acid to the alkali. swirl the flask to mix the contents. near the end, the indicator will start to change form pink to colourless. adjust the tap to add the alkali drop by drop near the end point. close the tap at eh end point and note the new burette reading. repeat until you get concordant results
what is the relative formula mass of a element
the sum of all the relative atomic masses of all the atoms in its formula.
how can you convert between g dm-3 and mol dm-3
> g dm^-3 to mol dm^-3 : divide the concentration by the relative formula mass > mol dm^-3 to g dm^-3 : multiply the concentration by the relative formula mass
how can the concentration of a solute in a solution be measured
it can be measured in g dm^-3 or in mol dm^-3.
how can you make a soluble salt from a soluble base
1) use an acid-base titration to find the exact volume of the soluble base that reacts with the acid. 2) mix the acid and soluble base in the correct proportions, producing a solution of the salt and water 3) warm the salt solution to evaporate the water, this will leave crystals of the salt behind
how can the amount of a substance be measured
grams, number of particles, or number of moles of particles.
what are the two types of hard water
temporary hardness and permanent hardness
how is permanent hardness caused, how is it removed
caused by substances such as calcium sulfate. unlike temporary hardness, permanent hardness cannot be removed by boiling the water. water can contain both types of hardness, so boiling may not remove all the hardness.
describe how you can make a soluble salt from an insoluble base
1) add an excess of insoluble base. 2) remove excess insoluble base by filtration. 3) evaporate to produce crystals of the salt.
how can water containing permanent hardness be softened using an ion exchange column
the column has little beads in it made from an ion exchange resin. hard water is sent through the column. as the water goes through, its calcium ions are swapped for sodium ions form the resin. sodium ions do not form scum with soap, so the water is softened.
what is removing hardness from water called
removing hardness from water is called softening
what are the problems associated with hard water
doesn’t easily form a lather when it is mixed with soap. the calcium ions and magnesium ions react with the soap, forming a precipitate. this precipitate is called scum and it causes soap to be wasted.
