VOLUMETRIC

VOLUMETRIC - Titration is a common laboratory method of...

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Unformatted text preview: Titration is a common laboratory method of quantitative chemical analysis that is used to determine the unknown concentration of a known reactant. Because volume measurements play a key role in titration, it is also known as volumetric analysis. Standard solution is a chemical term which describes a solution of known concentration . [see me for the lab, manual on standard soln.] Concentration 1. Mass conc ( conc. In gdm-3 ) :Mass (in grams) of a substance dissolved in 1dm-3 of solution. Mathematically; Mass(g) Vol(dm 3 ) Molar Conc (conc in moldm-3 ): amount of substance (in moles) present in 1dm 3 of solution. Mathematically; Molar conc = Note: Molar conc a.k.a MOLARITY (M) Amount, n (mol) Volume, V(dm 3 ) i.e. molar conc (M) = mass conc/molar mass Just like in solid no of mole = mass/molar mass Conc in moldm-3 = Conc in gdm-3 molar mass Concentration is just like sweetness of a solution. Imagine : A sugar solution contains 10.0g of sugar per dm 3 of solution and another contains 2.0g sugar per dm 3 of solution. The more concentrated one will be sweeter . Can you identify the sweeter? The conc. of a solution is directly proportional to the amount(mole,n) of substance in solution at constant volume. C n (V constant). The conc. (c) of a soln. is inversely proportional to the vol(V) of soln, if the amount(mole/mass) is constant. C 1/v (n constant). V V V V V C C C C C 1. A solution contains 2.65g of anhydrous Na 2 CO 3 in 200cm 3 of solution. Calculate the conc. of the soln in gdm-3 [Na 2 CO 3 = 106] Hint: Do you notice that the problem is given in 2.65g per 200cm 3 ?. Good! Just express it in gdm-3 . I mean gram in 1000cm 3 SIMPLE! Soln 200cm 3 of solution contain 2.65g of Na 2 CO 3 1000cm 3 of soln will contain X X = 1000cm 3 x 2.65g 200cm 3 X = 13.3g Simple arithmetic! Remember 1dm 3 = 1000cm 3 You can use this formula: Mass conc = mass(g)/vol(dm 3 ) [can you remember?] Mass = 2.65g(given), Vol in dm 3 = 200 1000 = 0.200dm 3 .: mass conc = 2.65 0.200 =13.25gdm 3 What is the molar conc . of a solution containing 1.12g of potassium hydroxide in 250cm3 of solution? [KOH = 56] Hint: molar conc. means ?????????? Conc. in mole per dm 3 Get your answer in gdm-3 and convert it to moldm-3 Then youve solved the problem 250cm3 contain 1.12g 1000cm3 will contain X X = 1000 x 1.12 250 X = 4.48gdm-3 Convert to molar conc. Molarity = mass conc molarmass = 4.48/56 = 0.080mol/dm 3 Using formular Molar conc = amnt (mol) Vol(dm 3 ) Mole = mass/Mm = 1.12/56 = 0.020mol Vol (dm 3 ) = 250/1000 = 0.250dm 3 Molar conc. = 0.020 0.250 = 0.080 mol/dm 3 What mass of sodium hydrogen trioxocarbonate (iv) NaHCO 3 would be required to prepare 100cm...
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VOLUMETRIC - Titration is a common laboratory method of...

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