Measuring mass accurately:In many experiments the best method for measuring mass is 1. Measure mass on (2 or 3d.p. ____) of a weighing ____ with the required quantity of solid in it 2. Empty mass into reaction ____ 3. ____ the now empty weighing bottle 4. ____ the mass of the empty weighing bottle from the first reading to give exact of mass actually ____. Diluting a solution Pipette ____ of original solution into a 250cm³ ____ flask •make up to the ____ with distilled water using a ____ pipette for last few drops. • ____ flask several times to ensure ____ solution. Using a volumetric ____ is more ____ than a measuring cylinder because it has a smaller ____. Use a teat pipette to make up to the mark in volumetric flask to ensure volume of solution ____ measured and one doesn’t go ____ the line Titrations •____ equipment (burette with ____, ____ with alkali, conical flask with ____ water) •pipette 25 cm³ of alkali into ____ flask •touch ____ of alkali with pipette ( to ensure correct amount is added) •adds acid solution from ____ •make sure the ____ space in the burette is filled with acid •add a few ____ of indicator and refer to colour change at end point •phenolphthalein ____ (alkali) to ____ (acid): end point pink colour just disappears use if NaOH is used •methyl orange ____ (alkali) to ____ (acid): end point orange use if HCl is used •use a ____ tile underneath the flask to help observe the ____ change •add acid to alkali whilst ____ the mixture and add acid drop wise at ____ point •note burette reading before and after addition of acid •repeats titration until at least 2 ____ results are obtained- two readings within ____ of each other Titration notes Distilled water can be added to the conical flask during a titration to wash the sides of the flask so that all the ____ on the side is ____ into the reaction mixture to react with the alkali. It does not affect the titration ____ as water does not react with the ____ or change the number of ____ of acid added. Recording results •Results should be clearly recorded in a ____ •Result should be recorded in full (i.e. both initial and final readings) •Record ____ volumes to 2dp (____ cm³ 0/5) Safety precautions Acids and alkalis are ____ (at low concentrations acids are ____) Wear ____ protection and gloves If spilled immediately ____ affected parts after spillage.

A level practical techniques

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