11. Molarity, volumes and the concentration of solutions See also 14.3 dilution of solutions calculations (a) Explaining the terms solubility, concentration, strength and molarity
TOP OF PAGE and sub-index (b) Measures of concentration and simple calculations of molarity (b)(i) Concentration in terms of mass of solute per unit volume of solution
A summary of how to do basic concentration calculations and rearrangement of the solution concentration formula
TOP OF PAGE and sub-index (b)(ii) Concentration in terms of moles of solute per unit volume of solution
A summary of how to do basic molarity calculations and rearrangement of the molarity formula
There are more questions involving molarity in section 12. on titrations
TOP OF PAGE and sub-index (c) APPENDIX 1 on SOLUBILITY and concentration calculations
TOP OF PAGE and sub-index (d) APPENDIX 2 - How to make up a standard solution - a solution of precisely known concentration The method and procedure of how to make up a standard solution of a soluble solid e.g. a salt, is fully described. Procedure for making up a standard solution of known molarity The method and procedure of how to make up a standard solution of a soluble solid e.g. a salt, is fully described
Example 1.
Example 2.
Procedure to make the standard solution i.e. one of known concentration of solid (in this case)
An accurate one pan electronic balanced is set to zero (preferably with an accuracy of two decimal places). A beaker is placed on the balance and the reading noted (ignore the figures on the diagram). Very carefully, with a spatula (not shown), salt crystals are added to the beaker until it weighs exactly 2.925 grams more than the beaker. This can be a very fiddly procedure if you want exactly 2.925g of salt. Pure water (distilled/deionised) is then added to the beaker to completely dissolve the salt and use of a stirring rod helps to speed up the process.
Eventually a clear solution of the salt should be seen, there should be no residual salt crystals at the bottom of the beaker or on the sides of the beaker.
An accurately calibrated 250cm3 volumetric flask should be washed out and cleaned several times with pure water.
Then, very carefully, the flask is topped up with pure water so the meniscus rests exactly on the 250.0cm3 calibration mark, a teat pipette is useful for the last few drops of water.
Job done! Note on standard solutions of acids and alkalis
TOP OF PAGE and sub-index (e) Self-assessment Quizzes on molarity calculations: type in answer QUIZ on molarity or multiple choice QUIZ on molarity type in titration answer QUIZ or multiple choice titration QUIZ
See also Advanced level GCE-AS-A2 acid-alkali titration calculation questions
Above is typical periodic table used in GCSE science-chemistry specifications in doing molarity calculations, and I've 'usually' used these values in my exemplar calculations to cover most syllabuses WHAT NEXT? e.g. OTHER CALCULATION PAGES
Page 2CALCULATIONS IN CHEMISTRY and quantitative chemical analysis Doc Brown's Chemistry KS4 science GCSE 9-1, IGCSE, O Level and GCE AS A2 Advanced A Level Revision Notes CHEMICAL CALCULATIONS INDEX PAGES of Online Quantitative Chemistry Calculations
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Answers to the more advanced level mole concept calculations Doc Brown's Chemistry - GCSE/IGCSE/GCE (basic A level) Online Chemical Calculations ANSWERS to Part 7 - the more advanced mole Q's The ORIGINAL mole Questions Index of all my online chemical calculation quizzes All my GCSE/IGCSE/US grade 8-10 Chemistry Revision notes Advanced UK A/AS level, IB and US grade 11-12 pre-university chemistry email doc brown Use your mobile phone or ipad etc. in 'landscape' mode This is a BIG website, you need to take time to explore it [ SEARCH BOX]Quantitative chemistry calculations This page has the answers to the more advanced mole based questions from calculations section 7. for more advanced chemistry students. Online practice exam chemistry CALCULATIONS and solved problems for KS4 Science GCSE/IGCSE CHEMISTRY and basic starter chemical calculations for A level AS/A2/IB. These revision notes and practice questions on how to do chemical calculations and worked examples should prove useful for the new AQA, Edexcel and OCR GCSE (9–1) chemistry science courses. Spotted any careless error? EMAIL query ? comment or request a type of GCSE calculation not covered? Mole calculations introduction * Molar gas volume * Advanced Redox titration Q's * Non-redox titration Q's Qa7.1 (a) f. mass Al2O3 = 102, 2 ÷ 102 x 3 x 6.02 x 1023 = 3.54 x 1022 oxide ions (b) f. mass H2 = 2, 3 ÷ 2 x 6.02 x 1023 = 9.03 x 1023 molecules (c) 1.2 ÷ 24000 x 6.02 x 1023 = 3.01 x 1019 molecules (d) f. mass Cl2 = 71, 3 ÷ 71 x 6.02 x 1023 = 2.54 x 1022 molecules (e) Neon exists as single atoms (Ar = 20), 10 ÷ 20 x 6.02 x 1023 = 3.01 x 1023 atoms (f) 2Na + 2H2O ==> 2NaOH + H2,or 0.104 dm3 (g) e.g. Mg + 2HCl ==> MgCl2 + H2
(h) both 1 mole of Na2CO3 or NaHCO3 will give 1 mole of CO2
(i) Zn + 2HCl ==> ZnCl2 + H2 , mole H2 = mole HCl ÷ 2
(j) CaCO3 + 2HCl ==> CaCl2 + H2O + CO2
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