EL7 (Ionic Equations + Titrations) Flashcards
When can’t an ionic equation be written?
If the products don’t change state.
What are the steps to writing an ionic equation for a reaction?
Write out the word equation, use this to write the symbol equation with state symbols, check that it’s balanced, split up the chemicals into their individual ions and write the charges, keep the state symbols, cancel out what doesn’t change state and rewrite the ionic equation underneath.
What are the rules for which ionic substances aren’t insoluble in water?
Barium, calcium, lead, and silver sulphate.
Silver and lead halides, (Cl,Br,I.)
All metal carbonates.
Metal hydroxides, except G1 and ammonium hydroxide.
What happens if ionic substances don’t dissolve?
They form a precipitate.
What are the 3 steps to working out the concentration of the unknown by using standard solutions and titrations?
1) Work out the moles of what you know.
2) Use the mole ratio to calculate moles of the other substance.
3) Answer the question, use the moles with the other value given.
Why is it necessary to weigh the weighing bottle after transferring the solid to the beaker?
So that this mass could be subtracted from the original mass before the solid was added to calculate how much of the solid was transferred.
Why shouldn’t solid be directly added to the volumetric flask?
Because it is harder to stir when it is in the flask so it is harder for it to dissolve as much.
Why is the beaker rinsed with distilled water and the washings also added to the VMF?
To ensure all the solid is transferred to the flask so the concentration is as accurate as possible.
Why is a dropper pipette used to add the last few drops of water to the flask?
To control how much water is added more precisely, so the bottom of the meniscus lies on the line on the neck of the flask.
Why is the flask inverted several times after the solid and distilled water has been added?
To ensure all the solid and distilled water is thoroughly mixed and dissolved so the concentration is even.
If some of the solid is dropped while transferring to the beaker, how would the concentration be affected?
The conc. would be lower because the mass would be lower in the same volume.
If the water meniscus is higher than the mark on the flask, how would concentration be affected?
Conc. would be lower as there is a larger volume for the same mass.
Why would the concentration be affected if the standard solution was made up using the hot flask?
The heat will have caused the glass to expand so it will be unable to measure the volume of the solution correctly.
What is a standard solution and why are they useful?
A solution of known concentration.
They can be used in a titration to work out the concentration of another concentration.
