(Solved): 7) Draw the Lewis structure of EDTA (figure 3) - include all the atoms and lone pairs. Circle all t ...

7) Draw the Lewis structure of EDTA (figure 3) - include all the atoms and lone pairs. Circle all the central atoms in the Lewis structure and state the molecular shape around each central atom. 8) In Part A.2, the standard \( \mathrm{Ca}^{2+} \) solution is provided as 200. ppm \( \mathrm{CaCO}_{3} \). In order to standardize the \( \mathrm{Na}_{2} \mathrm{H}_{2} \mathrm{Y} \), the molarity of \( \mathrm{Ca}^{2+} \) is needed. Convert 200. \( \mathrm{ppm} \mathrm{CaCO}_{3} \) to Molarity (mol/L) of \( \mathrm{Ca}^{2+} \). (This value will be needed for the report sheet, so have it ready before coming to lab.) graduated cylinder, \( 250 \mathrm{~mL} \) beakers (3), white sheet of paper, EDTA, Standardized \( \mathrm{CaCO}_{3} \) solution, buffer solution, EBT indicator (with \( \mathrm{Mg}^{2+} \) previously added), water sample (tap water). 1. Prepare the buret: a) Rinse a \( 50-\mathrm{mL} \) buret with 5 -mL portions of deionized water ( 3 times), making certain that the solution wets the entire inner surface. Then rinse the buret with the 5 - \( \mathrm{mL} \) of already prepared EDTA solution ( 2 times) in the same manner as the water. Check for any leakage or air bubbles. Discard the rinses in a waste container. b) Place the buret in the buret clamp with a \( 250 \mathrm{~mL} \) beaker below the buret. (Warning: Do not fill the buret by pouring solution above your head - lower the buret so that the solution and buret are at chest level.) Using a clean titration funnel, fill the buret with EDTA. Record the initial volume by reading the volume at the bottom of the meniscus (to 2 decimal place). 2. Prepare the Standard \( \mathrm{Ca}^{2+} \) solution - Obtain \( \sim 80 \mathrm{~mL} \) of standard \( \mathrm{Ca}^{2 *} \) solution in a clean beaker and record its precise Molarity on the report sheet. - Prepare three trials simultaneously and have ready before starting titration: i. From the \( -80 \mathrm{~mL} \) standard \( \mathrm{Ca}^{2+} \) solution, pipet \( 25.0 \mathrm{~mL} \) into each \( 125 \mathrm{~mL} \) Erlenmeyer flask ii. Add \( 1 \mathrm{~mL} \) of buffer solution to each flask \( (\mathrm{pH}=10) \) iii. Add 2 drops of EBT indicator (with Mg already added, Mg-EBT) to each flask - it should be wine red 3. Titrate the Standard \( \mathrm{Ca}^{2+} \) solution - Titrate the Standard \( \mathrm{Ca}^{2+} \) solution with the titrant, EDTA while swirling the Erienmeyer flask continuously. Near the endpoint, slow the rate of addition. The last few drops should be added at \( 3-5 \) second intervals. When the solution changes from wine-red to sky-blue the endpoint has reached. NOTE: End point comes quickly - Repeat the titration for the other two trials. - Discard the contents of Erlenmeyer flask in the sink and rinse flasks with deionized water to be used in part B.