Calculate how much [Co(NH3)5Cl]Cl2 is needed to prepare a 1.2*10^-2M solution in this experiment. In a bath set at 60 degree C thermostat for at least 15 minutes, two 100 mL volumetric flasks, one containing 0.10 N HNO_3 and the other 0.30 N HNO_3 solution (concentrated HNO_3 is approximately 15.9 M). To each solution add sufficient [Co(NH_3)_5 Cl]Cl_2 (prepared in the first week of the Cobalt Laboratory) to give a 1.2 times 10-2 M complex concentration. Shake the flasks until all of the complex has dissolved, and then return the flasks to the water bath. When the solution has again reached a temperature of 60 degree C (approximately 15 minutes), begin withdrawing samples with a pipette (use a rubber bulb, not your mouth!). Take ~ 3ml aliquot every 15 minutes from each reaction solution, and obtain 8 aliquots total during the course of the rate of study. Measure the absorption at 550nm on each sample immediately after removing it from the thermostatted solution and record the time of withdrawal.
The Correct Answer and Explanation is :
To prepare a (1.2 \times 10^{-2} M) solution of ([Co(NH_3)_5Cl]Cl_2) in a 100 mL volumetric flask, we need 0.321 g of the compound.
Explanation:
- Understanding the Required Concentration:
- The desired molarity is (1.2 \times 10^{-2} M), which means we need (1.2 \times 10^{-2}) moles of ([Co(NH_3)_5Cl]Cl_2) per liter of solution.
- Calculating Moles Required:
- Since we are preparing 100 mL (0.100 L) of the solution:
[
\text{Moles required} = (1.2 \times 10^{-2} \text{ M}) \times (0.100 \text{ L}) = 1.2 \times 10^{-3} \text{ moles}
]
- Determining Mass Required:
- The approximate molar mass of ([Co(NH_3)_5Cl]Cl_2) is 267.5 g/mol.
- The mass needed can be found using:
[
\text{Mass} = \text{Moles} \times \text{Molar Mass}
]
[
= (1.2 \times 10^{-3} \text{ moles}) \times (267.5 \text{ g/mol})
]
[
= 0.321 \text{ g}
]
Experimental Setup:
- Two 100 mL volumetric flasks are used, one containing 0.10 N HNO₃ and the other 0.30 N HNO₃.
- The calculated amount of 0.321 g of ([Co(NH_3)_5Cl]Cl_2) is added to each flask.
- The solutions are placed in a 60°C water bath for 15 minutes.
- Samples are withdrawn every 15 minutes for absorbance measurement at 550 nm to track the reaction kinetics.
Now, I will generate an illustrative image of the experimental setup.
The image illustrates the laboratory setup for the experiment, showing the volumetric flasks in a water bath, the pipette for sample collection, and the spectrophotometer for absorbance measurement at 550 nm. Let me know if you need any modifications or further explanations!
