Preparation For Inorganic Practical Flashcards
What is enthalpy change?
Heat change ÷ number of moles reacted.
How is heat change found?
Mass of solution (g)X 4.18 X temp change
What will the 3 different techniques all use?
A plastic cup held in a glass beaker with a thermometer.
What are the 3 techniques you may have to do?
Add measured amounts of reactants stir and record the starting and maximum temperatures
Record the temp of one solution for several minutes, add the other reagent and measure the temp over a long period of time. Draw the graph.
Measure the initial temp of one solution and add portions of other reactant at regular intervals, measuring the temp each time. A graph of temp against volume is drawn.
What must be avoided in technique?
Not stirring the mixture and not get the correct temp.
Give the readings to a correct amount of acuracy. It is usually to ± 0.1 degree so you may have to estimate. It also means you should always have a decimal point, even if it is 0.0
Don’t add to much solid. If gas is evolved, adding to much will result in it frothing over.
What are common errors in recording?
Failing to record masses to 0.01g. This means you must always have to decimal places, even if it is 1.00
Time must be recorded to an accuracy of at least a minute.
Record the temp for few minutes before adding the reactants to get a controle.
What are common errors in graph plotting?
A sensible scale must be chosen. Half of each axis should be used and the temperature axis should not start at 0˚
Label both axis.
Draw lines of best fit with a ruler.
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What should you assume the density’s of all solution are?
1 g cm³
Why would changing from a 1˚ thermometer to a 0.1 ˚ one not improve the accuracy of an experiment?
Error in reading temperature is less than the effect of ignoring heat loss
How is a soluble salt produced by using a solid or insoluble base?
And solid to acid. Filter out excess. Heat till volume reduced by half. Leave to cool and evaporate. Pick out crystals. Leave crystals to dry between 2 picks of tissue paper.
How is a soluble salt produced by using a soluble base?
Add the acid and alkali and use an indicator to see what volume neutralises what.
Repeat with out the indicator
Heat till volume reduced by half.
Leave to cool and evaporate.
Pick out crystals.
Leave crystals to dry between 2 picks of tissue paper.
How is an insoluble salt extracted from solution?
Remove salt through filtration.
Clean with distilled water to remove soluble impureities.
Dry on filter paper.
How do you know when an acid or alkali has been added in excess?
Use litmus paper to test the ph level.
