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How to answer a water of crystallisation question?
*find the hydrated(with water) mass *find the water mass *use this to find the anhydrous mass (hydrated- water) *calculate moles *divide larger by smaller mass
Suggest 2 modifications to the method of water of crystallisation that would reduce the percentage uncertainty in the mass residue?
*use larger mass of hydrated sodium chloride *increase mass balance to 3d.p
Is magnesium goes from +2 to +6 is it being oxidised or reduced and explain why ?
*oxidation *magnesium transfers 2 electrons
How could the student obtain a sample of magnesium phosphate after reacting magnesium with phosphoric acid ?
*filter to obtain solid/precipate *requires realisation that solid us filtered off *dry solid /evaporate the solution
Formula of an alkane and alkene
Alkane - CnH2n+2 Alkene - CnH2n
Describe the use of barium chloride in qualitative analysis?
*test for sulfate *white precipate forms
If 25cm3 of 0.200mol dm^3 of an acid is titrated when does then end point occur ?
It occurs when 25cm3 of acid has been added
What would result in a larger titre than it should be ?
Water is added to completely fill the volumetric flask rather than to the graduation line
What reagent would exactly neutralise 100cm3 of 1.00mol dm^3 of H2SO4
0.100 mol of Ba(OH)2
Predict the structure and bonding of BA2N2?
Giant ionic lattice structure
Describe how a student would prepare a solution of magnesium nitrate to start forming magnesium nitrate crystals?
*weight mass of the crystals (zero mass balance)with a balance and add to a crucible *dissolve in water *transfers to 250cm 3 volumetric flask * Make up to the mark with more water so that bottom of meniscus is on the mark *make sure u use a 3 do balance and use a an dropping pipette -use mcv and mol to find the mass for the question
How many dp are the figures in a tiration table?
Always put in 2 d.p
Suggest an improvement in making up a solution?
*use a 250cm3 volumetric flask instead of a beaker and rinse out the beaker with distilled water before transfer to volumetric flask *there is no weighing bottle u calculate the weight by calculating difference
Describe what a student needs to do to obtain reliable results for the titration?
Repeating the tiration to obtain a consistent/concordant result and calculate mean titre
A student prepares a solution of calcium nitrate from calcium carbonate what reagent is used and what is referred to as a reagent ?
• the reagent is the acid so it is nitric acid for this question
Describe and explain the change in the rate of the reaction in a graph?
*rate of the reaction decreases due to less frequent collisions
And how do I obtain the results from a rate of reaction graph?
*beaker *balance *stop watch *record mass at intervals Time intervals between 10-50s
How can you tell that salt has been formed in a reaction?
An hydrogen ion has been replaced by a metal ion
In titration what equipment measures the 25cm3 portion and makes up the acid solution to 250 cm3
*makes up acid - volumetric flask *measure the 25cm 3 portion - glass/graduated pipette
The student is not confident in the titre accuracy how could the student reduce random error ?
*repeat the tiration process until 2 titration are concordant *calculate mean tire from concordant titre
Example of a reaction between magnesium and water ?
Mg+2H2O ——>Mg(OH)2+H2
Example of a type of redox reaction?
Disproportionation