Information beforehand:
mass of weighing vial + NaCl / g 16.2597
mass of “empty” weighing vial / g 14.8136
mass of NaCl used / g
Final volume of solution / L 0.2500
Questions:
1) Calculate the concentration of the NaCl solution (in mol L-1 and with the correct number of significant digits).
2) Why is it desirable to use the same analytical balance to weigh the weighing vial + NaCl and to weigh the “empty” weighing vial?
3) Avoiding spilling the NaCl in the weighing vial is more important than getting all of the NaCl out of the vial. Why?
4) When transferring the dissolved NaCl from the beaker to the volumetric flask, all the glassware (beaker, stirring rod, funnel) are thoroughly rinsed with deionized water. Why?
1) Calculate the concentration of the NaCl solution (in mol L-1 and with the correct number of significant digits).
mols NaCl = grams/molar mass = 1.4461/58.4425 = 0.024744
M = mols/L = 0.024744/0.2500 = ? You are allowed 4 significant figures. That number is limited because of the 0.2500 number.
2) Why is it desirable to use the same analytical balance to weigh the weighing vial + NaCl and to weigh the “empty” weighing vial?
VERY good question. Just in case the weights are a little off in calibration, or some dirt is on one of the weights, or the balance was not zeroed properly or balanced properly or whatever, any errors caused by the vial + NaCl you hope will be the same error caused by the vial itself. Whatever error that is, when subtracted, will cancel. For example, let's just say you weighed an empty vial as 2.000 g because the weight was stamped as 2.000 g. Then you place some NaCl in it and the final weight is 2.150. The mass NaCl is 2.150-2.000 = 0.150 grams. Now let's say that the weight was dirty and that 2.000 g weight actually weighed 2.100 g (that's pretty dirty). Then when you added the NaCl the final weight was 2.250 grams. Now when you subtract 2.250 - 2.100 you get 0.150 grams and voila! That speck of dirt didn't mess up your analysis because you know the mass NaCl is 0.150 g in spite of the fact that the weight was dirty.
3) Avoiding spilling the NaCl in the weighing vial is more important than getting all of the NaCl out of the vial. Why?
Spilling the NaCl solid is more likely to lose more salt than if you leave a little in transferring. Actually, you shouldn't lose ANY in transferring because you can always wash that out and add it to the volumetric flask BEFORE make the flask to the mark with distilled water.
4) When transferring the dissolved NaCl from the beaker to the volumetric flask, all the glassware (beaker, stirring rod, funnel) are thoroughly rinsed with deionized water. Why?
You know that all of these utensils have some NaCl on the surface and that surface must be rinsed clean of any NaCl adhering to them.
1) The concentration of the NaCl solution can be calculated by dividing the mass of NaCl used by the final volume of solution. However, the mass of NaCl used is missing from the information provided, so I can't give you the exact concentration. But hey, just for fun, let's imagine the mass of NaCl used is 1 gram. In that case, the concentration of the NaCl solution would be (1g / 0.2500L) = 4 mol L-1. But remember, this is just a hypothetical scenario with a made-up mass of NaCl. Please be sure to check your actual calculations and use the correct mass.
2) It's desirable to use the same analytical balance for both weighing steps because the balance might get lonely if you don't give it equal attention. Plus, using the same balance ensures that any tare or calibration errors are consistent between the measurements. We wouldn't want the balance feeling left out or giving us inaccurate results, would we?
3) Avoiding spilling the NaCl in the weighing vial is more important because NaCl has a sneaky talent for hiding in unexpected places. Trust me, you'll find yourself seasoning your dinner with unintended saltiness if you spill it all over the place. So, it's better to be safe than to accidentally have a salty surprise in your food.
4) When transferring the dissolved NaCl from the beaker to the volumetric flask, it's important to rinse all the glassware with deionized water to remove any traces of NaCl. We don't want any leftover NaCl clinging to the glassware like a stubborn stain. It's like trying to get rid of a bad joke - you just want it gone! Rinsing ensures that we're not contaminating the solution or affecting its concentration. Plus, it's a good way to give the glassware a refreshing shower, because who doesn't like clean beakers and stirring rods?
1) To calculate the concentration of the NaCl solution, we need to first determine the moles of NaCl used.
Mass of NaCl used = mass of weighing vial + NaCl - mass of "empty" weighing vial
= 16.2597 g - 14.8136 g
= 1.4461 g
Next, we can determine the moles of NaCl by dividing the mass by the molar mass of NaCl. The molar mass of NaCl is 58.44 g/mol (sodium: 22.99 g/mol, chlorine: 35.45 g/mol).
Moles of NaCl = mass of NaCl used / molar mass of NaCl
= 1.4461 g / 58.44 g/mol
= 0.0248 mol
Finally, we can calculate the concentration of the NaCl solution by dividing the moles of NaCl by the volume of the solution in liters.
Concentration of NaCl solution = moles of NaCl / volume of solution
= 0.0248 mol / 0.2500 L
= 0.0992 mol L-1
To summarize, the concentration of the NaCl solution is 0.0992 mol L-1.
2) It is desirable to use the same analytical balance to weigh the weighing vial + NaCl and the "empty" weighing vial to ensure accuracy and consistency in the measurements. By using the same balance, any systematic error or variation in the balance can be eliminated or minimized, allowing for more precise and reliable measurements.
3) Avoiding spilling the NaCl in the weighing vial is more important than getting all of the NaCl out of the vial because spilled NaCl would result in a loss of mass, leading to an inaccurate measurement of the amount of NaCl used. It is crucial to accurately measure and record the mass of the NaCl to calculate the concentration of the solution correctly. Additionally, spilled NaCl may contaminate the surrounding area or interfere with other experiments or procedures.
4) When transferring the dissolved NaCl from the beaker to the volumetric flask, all the glassware (beaker, stirring rod, funnel) are thoroughly rinsed with deionized water to ensure that all the dissolved NaCl is transferred to the volumetric flask. This rinsing step helps to minimize any loss of the NaCl solution during the transfer process, ensuring that the final volume of the solution is accurately achieved. Additionally, rinsing the glassware with deionized water helps to remove any remaining traces of the NaCl solution, preventing contamination or interference with future experiments or procedures.
1) To calculate the concentration of the NaCl solution, we need to find the amount of NaCl used and the final volume of the solution.
To find the mass of NaCl used, we subtract the mass of the "empty" weighing vial from the mass of the weighing vial + NaCl:
Mass of NaCl used = Mass of weighing vial + NaCl - Mass of "empty" weighing vial
Mass of NaCl used = 16.2597 g - 14.8136 g = 1.4461 g
To find the concentration in mol L-1 (Molarity), we use the formula:
Molarity (M) = moles of solute / volume of solution (in L)
We need to convert the mass of NaCl used to moles. To do this, we divide the mass of NaCl used by its molar mass. The molar mass of NaCl is 58.44 g/mol (sodium has a molar mass of 22.99 g/mol, and chlorine has a molar mass of 35.45 g/mol):
Moles of NaCl = Mass of NaCl used / Molar mass of NaCl
Moles of NaCl = 1.4461 g / 58.44 g/mol = 0.0247 mol
Finally, we divide the moles of NaCl by the final volume of the solution in liters:
Concentration of NaCl solution = Moles of NaCl / Final volume of solution (in L)
Concentration of NaCl solution = 0.0247 mol / 0.2500 L = 0.0988 mol L-1
Therefore, the concentration of the NaCl solution is 0.0988 mol L-1.
2) It is desirable to use the same analytical balance to weigh the weighing vial + NaCl and to weigh the "empty" weighing vial to ensure accurate measurements. Using different balances may introduce systematic errors and inaccuracies. This is because the sensitivities, calibration, and precision of different balances can vary.
By using the same analytical balance, we eliminate the potential errors that can arise from inconsistencies between different balances. This allows for a more accurate measurement of the mass of the NaCl used, which is crucial when determining the concentration of the solution.
3) Avoiding spilling the NaCl in the weighing vial is more important than getting all of the NaCl out of the vial because accurately measuring the mass of the NaCl is essential for calculating the concentration of the solution.
If NaCl spills out during the transfer, the measured mass will be lower than the actual mass, leading to an incorrect calculation of the concentration. Even a small amount of lost NaCl can significantly affect the final result, as it can change the number of moles and subsequently the molarity of the solution. Minimizing spills ensures accurate measurements and reliable concentration calculations.
4) When transferring the dissolved NaCl from the beaker to the volumetric flask, it is important to rinse all the glassware (beaker, stirring rod, funnel) with deionized water. This is done to ensure that all the dissolved NaCl is transferred to the volumetric flask and to prevent any loss or contamination.
Rinsing the glassware with deionized water helps to remove any remaining traces of NaCl from the surfaces, ensuring a more accurate transfer of the solution. It also helps in diluting any remaining NaCl solution stuck to the sides of the glassware, increasing the overall concentration accuracy.
By rinsing all the glassware, we can achieve a complete transfer of the dissolved NaCl and maintain the desired concentration in the final solution. Additionally, it helps prevent the contamination of the solution with impurities that might be present on the glassware surfaces, ensuring the purity and accuracy of the solution.