As a part of a study to see whther just the chloride ion on NaCl accelerates the rusting of iron, a student decided to see whtjer iron rusted in a solution on Na2SO4. The solution was made by dissolving 4.550 g of Na2SO4 in water using 125.0 mL volumetric flask to adjust the final volume. What is the molarity of the solution?
I don't understand this question at all. What do you do with the iron :S
Actually, the question isn't stated very well but what they mean is that 4.550 g Na2SO4 are dissolved in a total volume of 125 mL. They want you to calculate the molarity. To do this, just remember the definition of molarity. It is the number of moles per liter of solution.
So you use 4.550 g Na2SO4, calculate the moles in that mass, then moles/L (the L is 0.125 ) gives the molarity.
mass = 4.550 g
molar mass = 142.05 g/mol
n= 0.032030975 mol
c= 0.032030975/0.125 = 0.256 mol/L
would I have 3 or 4 sig. digs? cause when I converted 125.0mL into 0.125 L I lost a sig dig;or should it be 0.1250 L?
You have 4 s.f. in 4.550.
There are 6 s.f. in 142.043 which I used instead of 142.05).
There are 4 s.f. in 125.0 mL (or 0.1250).
Therefore, you are allowed 4 s.f. (from the lowest which is 0.1250 or 4.550) so the answer is 0.25626 moles/L which rounds to 0.2563 M to 4 s.f. [I take issue, somewhat, that you lose one place when converting 125.0 to 0.1250. I see 4 s.f. in both 125.0 as well as in 0.1250.]
Thank you so much :)
To find the molarity of the solution, we need to first calculate the number of moles of Na2SO4 present in the solution, and then divide it by the volume of the solution in liters.
To calculate the number of moles of Na2SO4, we need to divide the given mass of Na2SO4 by its molar mass. The molar mass of Na2SO4 is calculated by adding the atomic masses of sodium (Na), sulfur (S), and oxygen (O).
The atomic masses of Na, S, and O are:
Na = 22.99 g/mol
S = 32.07 g/mol
O = 16.00 g/mol
To calculate the molar mass of Na2SO4:
Molar mass = 2(Na) + S + 4(O)
Molar mass = 2(22.99) + 32.07 + 4(16.00)
Molar mass = 45.98 + 32.07 + 64.00
Molar mass = 142.05 g/mol
Next, we calculate the number of moles of Na2SO4 by dividing the given mass (4.550 g) by its molar mass:
moles of Na2SO4 = mass of Na2SO4 / molar mass of Na2SO4
moles of Na2SO4 = 4.550 g / 142.05 g/mol
Now we need to convert the volume of the solution from milliliters to liters. There are 1000 mL in 1 L, so dividing the given volume (125.0 mL) by 1000 will give us the volume in liters:
volume of solution = 125.0 mL / 1000
volume of solution = 0.125 L
Finally, we can calculate the molarity of the solution by dividing the moles of Na2SO4 by the volume of the solution in liters:
Molarity (M) = moles of Na2SO4 / volume of solution (in L)
By plugging in the values, we can calculate the molarity of the solution.