Lab 5

Concentration vs. Transmitted Light Through a Solution

Unit 5⏱ 90 minGuided Inquiry

Overview

What is the relationship between the concentration of a solution and the amount of transmitted light through the solution?

Objectives

What is the relationship between the concentration of a solution and the amount of transmitted light through the solution?
Connect observations to AP Chemistry models and calculations.

⚠️ Wear protective goggles and an apron. Follow your teacher’s safety directions for all chemicals and equipment.

Materials Needed

Cobalt (II) chloride hexahydrate distilled water balance -mL volumetric pipet disposable pipets Kimwipes, four 100-mL volumetric flasks weighing boats spectrophotometer 25-mLvolumetric pipet cuvettes labels -mL volumetric pipet Pipette pump beakers Always wear safety goggles. Wash hands before leaving the lab

Procedure

Part A – Solutions and Dilutions Using a balance, weigh out enough CoCl2·6H2O (Cobalt (II) chloride hexahydrate) to make a 0.080M Stock Solution in a 100-mL volumetric flask.

Using your 0.080M Stock solution, make the following dilutions using volumetric pipets ONLY.

(Do NOT use graduated cylinders): 0.020M in a 100-mL volumetric flask, 0.016M in a 100-mL volumetric flask, 0.0080 M in a 100-mL volumetric flask Label the top of all four volumetric flasks with the concentration and your group name.

Part B – Using a Spectrophotemeter Turn on the Spectrophotometer and let it warm up for 15 minutes.

Set the wavelength to 510 nm using the Wavelength Dial.

Set the Filter Position Lever to 340-599 nm.

Using the 0%T Dial, set the % Transmittance to read 0.0.

Fill a cuvette with distilled water.

Clean the outside of the cuvette with a Kimwipe to remove oil from fingerprints left on the cuvette.

Insert the cuvette correctly into the cuvette slot.

(See Teacher for help).

Use the 100%T / 0A Dial to set the Transmittance to read 100.0.

Pre-Lab Questions