The most common way to prepare a sample for analysis by atomic spectroscopy is to dissolve it (using acid digestion or appropriate solvents), filter the solution and dilute appropriately. The sample reading is then compared to a standard or series of standard solutions. The preparation of accurate analytical solutions is key to the success of the analysis. Very small quantities (either volumes or weights) can introduce uncertainty and inaccuracy. Indicate how you would prepare the following solutions accurately in the laboratory. (9 marks, 3 each) a) 500 mL of a 0.1500 M solution of phosphate ions from solid K$_2$HPO$_4$ b) 500 mL of a stock solution containing 40 ppm of potassium ions from
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To do this, use the formula: moles = Molarity (M) x Volume (L) moles = 0.0250 M x 0.100 L moles = 0.0025 mol Show more…
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(a) Potassium iodate solution was prepared by dissolving 1.022 g of KIO3 (FM 214.00) in a 500 mL volumetric flask. Then 50.00 mL of the solution was pipetted into a flask and treated with excess KI (2 g) and acid (10 mL of 0.5 M H2SO4). How many millimoles of I3− are created by the reaction? ANSWER is 1.433 mmol (b) The triiodide from part (a) reacted with 37.54 mL of Na2S2O3 solution. What is the concentration of the Na2S2O3solution?
Shaiju T.
You choose to investigate some of the solubility guidelines for two ions not listed in Table $4.1,$ the chromate ion $\left(\mathrm{CrO}_{4}^{2-}\right)$ and the oxalate ion $\left(\mathrm{C}_{2} \mathrm{O}_{4}^{2-}\right) .$ You are given $0.01 \mathrm{M}$ solutions (A, B, C, D) of four water-soluble salts: $$ \begin{array}{lll} \hline \text { Solution } & \text { Solute } & \text { Color of Solution } \\ \hline \text { A } & \mathrm{Na}_{2} \mathrm{CrO}_{4} & \text { Yellow } \\ \mathrm{B} & \left(\mathrm{NH}_{4}\right)_{2} \mathrm{C}_{2} \mathrm{O}_{4} & \text { Colorless } \\ \mathrm{C} & \mathrm{AgNO}_{3} & \text { Colorless } \\ \mathrm{D} & \mathrm{CaCl}_{2} & \text { Colorless } \\ \hline \end{array} $$ When these solutions are mixed, the following observations are made: $$ \begin{array}{lll} \hline \text { Expt } & \text { Solutions } & \\ \text { Number } & \text { Mixed } & \text { Result } \\ \hline 1 & \mathrm{~A}+\mathrm{B} & \text { No precipitate, yellow solution } \\ 2 & \mathrm{~A}+\mathrm{C} & \text { Red precipitate forms } \\ 3 & \mathrm{~A}+\mathrm{D} & \text { Yellow precipitate forms } \\ 4 & \mathrm{~B}+\mathrm{C} & \text { White precipitate forms } \\ 5 & \mathrm{~B}+\mathrm{D} & \text { White precipitate forms } \\ 6 & \mathrm{C}+\mathrm{D} & \text { White precipitate forms } \end{array} $$ (a) Write a net ionic equation for the reaction that occurs in each of the experiments. (b) Identify the precipitate formed, if any, in each of the experiments.
Experiment: Standardization of sodium hydroxide stock solution with potassium hydrogen phthalate You prepare a solution by dissolving 4.8854 g of KHP (molar mass: 204.23 g/mol) in distilled water and making it up to 250 mL in a volumetric flask. You pipette 25 mL of the solution, add phenolphthalein indicator, and then perform 3 separate titrations using NaOH. The average volume of NaOH added is 23.97 mL. The chemical equation for the reaction between aqueous NaOH solution and potassium hydrogen phthalate is: KHP (aq) + NaOH (aq) -> NaKP + H2O. Calculate the following (please show detailed calculations): a) The number of moles of KHP b) The molarity of KHP solution c) The molarity of the NaOH solution
David C.
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