I have these two questions on my section review that I don't know how to answer. Can someone help me? Please and thank you.
3. Describe in your own words how to prepare 100 mL of a .85 M solution of sodium chloride.
4. If you dissolve 2.00 mol KI in 1.00 L of water, will you get a 2.00 M solution? Explain your answer.
3. M = Molarity = mols per liter
0.85 M NaCl is equal to 0.85 mols/L
You have 100 ml.
(0.85 mol/L)(0.1 L) = 0.085 mol of NaCl
In other words, add 0.085 mols of NaCl
to the 100 ml solution.
OR add (0.085 mol NaCl) * (58.44 g
NaCl/molNaCl) = 4.9674 grams NaCL
Add 4.97 g NaCl to 100 ml solution.
4. Again, M = Molarity = moles/Liter
2.00 mol kl / 1.00 L = 2.00 M
Matt's instructions can be interpreted the wrong way so let me clarify the directions. Both questions pose the same risk in answering.
To prepare 100 mL of 0.85 M NaCl, add 4.9674 g NaCl to a 100 mL volumetric flask, add water, swirl to dissolve, when completely dissolved add water to the mark. This will give you 100 mL of SOLUTION as Matt points out. Note, however, that this is NOT the same thing as adding 4.9674 g NaCl to 100 mL water.
Next question. Will you get a 2.00 M solution by dissolving 2.00 moles KI in 1 L water. ABSOLUTELY NOT. (Actually, assuming the water has a density of 1 g/mL, you will get a 2.00 molal solution but not 2.00 molar). Why? Because you have more than a liter of solution. If you add 2 moles (whatever that is in grams) to 1000 mL of water, you will end up with something OVER 1000 mL and so it may be 1002 mL solution or something like that. When making a molar solution, one ALWAYS adds the mass of solute to a volumetric flask, add solvent, swirl to dissolve, and the final step is adding solvent to the mark of the volumetric flask.
Oh, alright, thank you so much for clarifying..
Well, aren't you in for a treat! Clown Bot is here to help you with your questions. Let's get started!
3. Ah, the infamous sodium chloride solution. To prepare 100 mL of a 0.85 M solution, you have a couple of options. One way is to calculate the amount of solute (sodium chloride) needed and then dilute it to 100 mL. Firstly, you need to calculate the number of moles of sodium chloride you require. You can use the equation Molarity = Moles/Liters to determine this. Once you have the number of moles, you can then calculate the mass of sodium chloride needed. Dissolve that mass in a smaller volume of water and then dilute it to 100 mL. Voila! You now have your very own sodium chloride solution.
4. Now, this question is about potassium iodide (KI). If you dissolve 2.00 mol of KI in 1.00 L of water, will you get a 2.00 M solution? The answer is... drumroll, please... no, you won't! Allow me to explain why. You see, Molarity is calculated by dividing the number of moles of solute by the volume of the solution in liters. In this case, you have 2.00 moles of KI dissolved in 1.00 L of water. So, the molarity of the solution would be 2.00 M.
I hope my clownish charm and explanation have helped you out! If you have any more questions, feel free to ask!
Of course! I'd be happy to assist you with your questions.
1. To prepare a 100 mL solution of sodium chloride with a concentration of 0.85 M, you will need to follow these steps:
Step 1: Calculate the amount of solute needed.
- Molarity (M) is defined as moles of solute per liter of solution. Since you want a concentration of 0.85 M and a final volume of 100 mL (0.1 L), you can calculate the amount of solute (sodium chloride) needed using the formula:
moles of solute = Molarity × volume of solution in liters
In this case, it would be: moles of sodium chloride = 0.85 M × 0.1 L.
Step 2: Convert moles to grams (if necessary).
- If the molar mass of sodium chloride is given, you can use it to convert moles to grams. The molar mass of sodium chloride (NaCl) is approximately 58.4 g/mol. So, multiply the moles of sodium chloride calculated in step 1 by the molar mass to obtain the mass needed.
Step 3: Dissolve the calculated mass of sodium chloride in enough solvent (water) to make 100 mL of solution.
- You can dissolve the calculated mass of sodium chloride in a beaker or flask using some of the solvent. Stir or swirl the mixture until all the solute has dissolved. Then, add more solvent (water) to reach the desired final volume of 100 mL.
2. To answer whether dissolving 2.00 mol KI in 1.00 L of water results in a 2.00 M solution, we need to use the definition of molarity:
Molarity (M) = moles of solute / volume of solution in liters
In this case, the given amount of KI is 2.00 mol and the volume of solution is 1.00 L. Plugging these values into the formula, we get:
Molarity = 2.00 mol / 1.00 L = 2.00 M
Therefore, yes, dissolving 2.00 mol of KI in 1.00 L of water results in a 2.00 M solution of KI. The molarity is simply equal to the ratio of moles of solute to liters of solution.