How would you prepare each of the following solutions?
a. 100mL of a 155ppm solution of urea, CH4N2O, in water.
b.100mL of an aquaneous solution whose K+ concentration is 0.075M
To prepare each of the solutions mentioned, you need to follow the appropriate steps for the given compounds. Let's break it down:
a. 100mL of a 155ppm solution of urea, CH4N2O, in water.
To prepare this solution, you will need to weigh out the appropriate amount of urea and dissolve it in water to achieve the desired concentration.
Step 1: Determine the mass of urea needed:
To calculate the mass of urea required for a specific concentration, you need to know the molar mass of urea (CH4N2O) and the desired concentration in ppm (parts per million).
- The molar mass of urea is 60.06 g/mol.
- ppm can be converted to mg/L (milligrams per liter) since 1 ppm = 1 mg/L.
For example, to prepare a 100mL solution with a concentration of 155ppm:
Concentration in mg/L = 155 mg/L
Mass in grams = [(Concentration in mg/L) / (1000 mg/g)] * (Volume in liters)
= [(155 mg/L) / (1000 mg/g)] * (0.100 L)
= 0.0155 g
Therefore, you need 0.0155 g of urea to prepare a 100mL solution with a concentration of 155ppm.
Step 2: Dissolve urea in water:
Once you have measured the appropriate mass of urea, transfer it to a container and add water to make a total volume of 100mL. Stir the solution until the urea has completely dissolved. Make sure the container is clean and dry before use.
b. 100mL of an aqueous solution whose K+ concentration is 0.075M.
To prepare this solution, you need to know the molar mass of K+ and use it to determine the appropriate amount of a potassium compound that can dissolve in water to achieve the desired concentration.
Step 1: Determine the mass of potassium compound needed:
To calculate the mass of the potassium compound required, you need to know the molar mass of K+ (usually obtained from a compound like potassium chloride, KCl).
- The molar mass of K+ is 39.10 g/mol.
To prepare a 100mL solution with a concentration of 0.075M:
Mass in grams = (Concentration in mol/L) * (Volume in liters) * (molar mass in g/mol)
= (0.075 mol/L) * (0.100 L) * (39.10 g/mol)
= 0.293 g (rounded to three decimal places)
Therefore, you need approximately 0.293 g of a potassium compound, like potassium chloride (KCl), to prepare a 100mL solution with a K+ concentration of 0.075M.
Step 2: Dissolve the compound in water:
Once you have measured the appropriate amount of the potassium compound, dissolve it in water to make a total volume of 100mL. Stir the solution until the compound has completely dissolved. Ensure the container is clean and dry before use.
Remember, it's important to handle chemicals safely and wear appropriate protective equipment when working with them. Also, always follow any specific instructions or guidelines provided by a laboratory or supervisor when preparing solutions.