i want to know how to work out the initial concentration of OH- mol/litre of eac

Question

i want to know how to work out the initial concentration of OH- mol/litre of each of these samples prepared

The object of this experiment is to determine the kinetics of this slow reaction (see Prof Curran lectures) whose rate has been shown to be equal to klP TIOH 1. Experimental 1. Working INDIVIDUALLY prepare 250.0 ml of a -0.300 mol dm solution of sodium chloride. 2. Prepare the following mixtures from the stock solutions of 0.300 mol dm NaOH (provided) and th NaCl (prepared by you in 1 above): in a 100.0 ml volumetric make up solutions containing 75.0 ml of stock NaOH + the balance NaCI; 50.0 ml of NaOH +NaCI and finally (ii) 25.0 ml NaOHthe balance NaCI. . Nearly fill a 1 cm cuvette with the 0.300 mol dm23 solution of NaOH provided to you, add I drop o Place the cuvette in a spectrometer and monitor the change in initial absorbance of the cell as a funct of time (use a stopwatch and record absorbance every 30 seconds for approximately 3 minutes)a huachuce is within the scale of the instrument (i dilute solution of phenolphthalein in ethanol, cap the cuvette and invert rapidly to mix thoroughly.

Explanation / Answer

Conversion Factor

1 L = 1 dm^3

Hence we can write the concetration of 0.300 mol dm^(-3) = 0.300 M

Stock solution = 250 mL, Molarity of stock solution = 0.300M

Solution 1: 75 mL of stock NaOH + the balance NaCl (Total volume - 100 mL)

Number of moles of NaOH = Volume of stock solution (in L) * Molarity = 75/1000 * 0.300 = 0.0225 moles

Molarity = Number of moles of solute/Volume of solution = 0.0225 mol/0.1 L = 0.225 M

Solution 2: 50 mL of stock NaOH + the balance NaCl (Total volume - 100 mL)

Number of moles of NaOH = Volume of stock solution (in L) * Molarity = 50/1000 * 0.300 = 0.0150 moles

Molarity = Number of moles of solute/Volume of solution = 0.0150 mol/0.1 L = 0.150 M

Solution 3: 25 mL of stock NaOH + the balance NaCl (Total volume - 100 mL)

Number of moles of NaOH = Volume of stock solution (in L) * Molarity = 25/1000 * 0.300 = 0.0075 moles

Molarity = Number of moles of solute/Volume of solution = 0.0075 mol/0.1 L = 0.075 M

Related Questions

Navigate

• Browse (All)
• Browse I
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.