GENERAL CHEMISTRY 1140 SOLUTION CONCENTRATION - MOLARITY PREPARATION DILUTION TITRATIONS MEASURING REAGENTS MOST SOLIDS CAN BE WEIGHED ACCURATELY BUT..... HCl IS A GAS! NaOH CAN'T PURCHASE 100% PURE MANY REACTIONS HAVE TO BE RUN BY ADDING ONE SOLUTION TO ANOTHER AgNO3(s) + NaCl(s) ---> No Reaction AgNO3(aq) + NaCl(aq) ---> AgCl(s) + NaNO3(aq) MEASURE VOLUME OF A SOLUTION USING GRADUATED CYLINDERS, MOHR PIPETS, VOLUMETRIC PIPETS, VOLUMETRIC FLASKS. IF WE USE A SOLUTION WE NEED TO KNOW HOW MUCH OF THE REACTANT IS IN THE SOLUTION? WE NEED A CONCENTRATION OF THE SOLUTION! MOLARITY = M A ONE MOLAR SOLUTION HAS ONE MOLE OF SOLUTE DISSOLVED IN ONE LITER OF SOLUTION 1 M = 1 mol/1 liter = 1 mol/L 3.07 M = 3.07 mol/L ASSUME I HAVE ONE LITER OF A ONE MOLAR SOLUTION OF NaCl ASSUME I POUR 500 mL OF THE SOLUTION INTO A 500mL CONTAINER WHAT IS THE CONCENTRATION OF THE SOLUTION IN THE 500 mL CONTAINER? IF I HAVE 100 mL OF A 1 M HCl SOLUTION, HOW MANY MOLES OF HCl DO I HAVE?
IF I HAVE 75 mL OF A 2.0 M NaOH SOLUTION, HOW MANY MOLES OF NaOH DO I HAVE?
WHAT IS THE MOLARITY OF A 500.0 mL SOLUTION PREPARED FROM 18.2 g NaOH? MOLARITY = MOLES/LITER FIND MOLES AND FIND LITERS!!!
YOU NEED 100.0 mL OF A 0.478 M SODIUM HYDROXIDE SOLUTION. HOW MUCH SOLID SODIUM HYDROXIDE MUST YOU WEIGH OUT?
PROBLEMS: YOU CANNOT OBTAIN PURE SODIUM HYDROXIDE SOLID SODIUM HYDROXIDE PICKS UP MOISTURE FROM THE AIR PREPARE A CONCENTRATED SOLUTION AND DILUTE IT! HOW MUCH 6.00 M NaOH IS REQUIRED TO PREPARE 100.0 mL OF 0.478 M SODIUM HYDROXIDE SOLUTION?
NOTE: A 0.200 M SOLUTION OF SODIUM SULFATE WOULD BE: 0.400 M IN SODIUM ION 0.200 M IN SULFATE ION VOLUMETRIC ANALYSIS USING TITRATIONS ASSUME WE NEED SEVERAL HUNDRED MILLILITERS OF ABOUT 0.2 M NaOH SOLUTION SIMPLY DISSOLVE 4 g NaOH IN ABOUT 500 mL SOLUTION
WHAT IF WE NEED THE CONCENTRATION TO FOUR SIGNIFICANT FIGURES? WE DON'T HAVE PURE, SOLID NaOH NEUTRALIZE NaOH WITH A 100% PURE ACID FROM THE BALANCED EQUATION WE CAN RELATE MOLES OF ACID TO MOLES OF BASE CERTAIN COMPOUNDS (INDICATORS) TURN COLOR WHEN CHANGE FROM ACID TO BASE COLOR CHANGE INDICATES WHEN ALL THE ACID HAS BEEN REACTED CALLED THE END POINT OR STOICHIOMETRIC POINT
USE A BURET TO ACCURATELY MEASURE VOLUME OF NaOH
PLUS OR MINUS 0.02 mL ---> 4 SIGNIFICANT FIGURES!!! PROCESS IS CALLED TITRATION TO DETERMINE ACCURATELY THE CONCENTRATION OF THE APPROXIMATELY 0.2 M SOLUTION WEIGHED 1.134 g (4 SF) OF KHC8H8O4 (POTASSIUM ACID PHTHALATE = KHP) 100.00 % PURE HC8H8O41- + OH1- ---> H2O + C8H8O42IT TOOK 28.47 mL OF THE NaOH FOR THE COLOR TO CHANGE (NEUTRALIZATION) MOLARITY = MOLES/LITER GRAMSKHP RELATED TO MOLESNaOH WE HAVE THE VOLUME OF NaOH
WHAT IS THE PERCENT IRON IN A 1.327 g IRON ORE SAMPLE WHICH REQUIRED 18.12 mL OF A 0.1371 M POTASSIUM PERMANGANATE SOLUTION TO TITRATE? NEED SOME CHEMISTRY Fe2O3 + HClO4 ---> Fe3+ Fe3+ + Zn ---> Fe2+ 5 Fe2+ + MnO41- + 8 H1+ ---> Mn2+ + 5 Fe3+ + 4H2O CALCULATIONS
CALCULATE %
A detailed description of the titration process is available here. | Chemistry Home | Dr. Sundin Home |
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