A 5.0 g sample of Cu(NO3)2-nH20 is heated, and 3.9 g of the anhydrous salt remains. What is the value of n?
I got as far as finding the molar mass of Cu(NO3)2, which is 187.5g/mol
Please help me further with this question.
g Cu(NO3)2 = 3.9
g H2O = 5.0-3.9 = 1.1
mols Cu(NO3)2 = 3.9/187.5 = 0.0208
mols H2O = 1.1/18 = 0.0611
You want n mols H2O/1 mol Cu(NO3)2
So 1 mol Cu(NO3)2 = 0.0208/0.0208 = 1.000
n mols H2O = 0.0611/0.0208 = 2.94. Round that to a whole number of 3.0
Formula is Cu(NO3)2*3H2O
I didn't understand....please explain in detail
I also did not understand.Please make it in a little bit easier way:)
Hey there! Let's solve this problem together, but don't worry, I won't make chemistry too dry for you!
To find the value of n, we need to calculate the number of moles of Cu(NO3)2 and the moles of H2O lost during the heating process.
Given that the mass of the anhydrous salt is 3.9 g, and its molar mass is 187.5 g/mol, we can find the number of moles of Cu(NO3)2 using the formula:
moles = mass / molar mass
So, moles of Cu(NO3)2 = 3.9 g / 187.5 g/mol
Now, to find the moles of water lost, we need to calculate the difference between the initial mass (5.0 g) and the mass of the anhydrous salt (3.9 g). Let's call the moles of water lost "x."
moles of water lost = mass lost / molar mass of water
mass lost = initial mass - mass of anhydrous salt
= 5.0 g - 3.9 g
Now, let's calculate the moles of water lost using the molar mass of water (18 g/mol):
moles of water lost = (5.0 g - 3.9 g) / 18 g/mol
So, now we have the moles of Cu(NO3)2 and the moles of water lost. Since one mole of Cu(NO3)2 contains six moles of water, we can set up a ratio:
moles of Cu(NO3)2 / moles of water lost = 1 / 6
Substituting the values we calculated:
(3.9 g / 187.5 g/mol) / (x mol / 18 g/mol) = 1 / 6
Now, we can solve for x:
(3.9 g * 18 g/mol) / (187.5 g/mol) = x / 6
Solving this equation gives us:
x = (3.9 g * 18 g/mol * 6) / 187.5 g/mol
After doing the math, we find that x is approximately 0.748 mol.
Therefore, the value of n is approximately 0.748.
Keep in mind that this is just an approximate value due to rounding off. But I hope this explanation helped, and remember, chemistry is all about having the right reaction!
To solve for the value of n in Cu(NO3)2-nH2O, we can use the concept of the Law of Conservation of Mass. According to this law, the mass of reactants should be equal to the mass of products in a chemical reaction.
In this case, we are given that a 5.0 g sample of Cu(NO3)2-nH2O is heated and 3.9 g of the anhydrous (without water) salt remains. We want to find the value of n, which represents the number of water molecules attached to each Cu(NO3)2 unit.
First, we need to determine the mass of Cu(NO3)2 in the original sample. From the formula Cu(NO3)2-nH2O, we know that the molar mass of Cu(NO3)2 is 187.5 g/mol.
Using the molar mass, we can find the moles of Cu(NO3)2 in the initial sample:
moles of Cu(NO3)2 = mass / molar mass
moles of Cu(NO3)2 = 5.0 g / 187.5 g/mol
Next, we need to determine the mass of Cu(NO3)2 in the remaining sample. Since we are given that 3.9 g of anhydrous salt remains, the mass of Cu(NO3)2 is the same as the remaining sample.
Using the moles of Cu(NO3)2, we can find the mass of Cu(NO3)2 in the remaining sample:
mass of Cu(NO3)2 = moles of Cu(NO3)2 × molar mass
mass of Cu(NO3)2 = moles × 187.5 g/mol
mass of Cu(NO3)2 = (5.0 g / 187.5 g/mol) × 187.5 g/mol
Now, we have the mass of Cu(NO3)2 in both the initial and remaining sample. Since the remaining sample is the anhydrous form (without water), the mass difference between the two samples is due to the loss of water molecules.
Therefore, we can calculate the mass of water lost:
mass of H2O lost = mass of Cu(NO3)2 in initial sample - mass of Cu(NO3)2 in remaining sample
mass of H2O lost = (5.0 g / 187.5 g/mol) × 187.5 g/mol - 3.9 g
Finally, to find the value of n (the number of water molecules attached to each Cu(NO3)2 unit), we need to convert the mass of water lost to moles of water. Since the molar mass of water (H2O) is 18.0 g/mol, we can calculate the moles of water using:
moles of H2O lost = mass of H2O lost / molar mass of H2O
moles of H2O lost = (mass of H2O lost) / 18.0 g/mol
The resulting value of moles of H2O lost will give us the value of n in Cu(NO3)2-nH2O.