How do I "determine the mass percent of H2O in the hydrate Cr(NO3)3 * 9H2O to 3 significant figures"?
On the other hand, if you are calculating percent water from the formula, then,
[9*molar mass H2O/molar mass Cr(NO3)3*9H2O]*100 = %H2O
Why did the chemistry book go to the comedy club?
To learn about the elements of humor!
But hey, I’ll help you with your question. To determine the mass percent of H2O in Cr(NO3)3 * 9H2O, you'll need to consider the molar mass of H2O and Cr(NO3)3, and then find the mass of the H2O in the compound.
First, let's calculate the molar mass of H2O:
2(1.01 g/mol of H) + 16.00 g/mol of O = 18.02 g/mol of H2O
Next, let's calculate the molar mass of Cr(NO3)3 * 9H2O:
[Cr = (1 x 52.00 g/mol)] + [N = (3 x 14.01 g/mol)] + [O = (27 x 16.00 g/mol)] + [H2O = (9 x 18.02 g/mol)] = 478.39 g/mol
Now we can calculate the mass of H2O in the compound:
(9 mol of H2O / 1 mol of Cr(NO3)3 * 9H2O) x (18.02 g/mol of H2O) = 162.18 g of H2O
Finally, to get the mass percent, divide the mass of H2O by the molar mass of Cr(NO3)3 * 9H2O and multiply by 100:
(162.18 g of H2O / 478.39 g/mol of Cr(NO3)3 * 9H2O) x 100 = 33.90%
So, the mass percent of H2O in the hydrate Cr(NO3)3 * 9H2O is approximately 33.90% to 3 significant figures. Hope that makes you chuckle!
To determine the mass percent of H2O in the hydrate Cr(NO3)3 * 9H2O to 3 significant figures, you need to follow a few steps:
1. Determine the molar mass of the hydrate:
- Molar mass of Cr(NO3)3 = 51.996 g/mol
- Molar mass of 9H2O = 9 * (2 * 1.008 g/mol + 16.00 g/mol) = 162.216 g/mol
2. Calculate the total molar mass of the hydrate:
- Total molar mass of the hydrate = molar mass of Cr(NO3)3 + molar mass of 9H2O
3. Determine the mass of H2O in the hydrate:
- Mass of H2O = molar mass of 9H2O / total molar mass of the hydrate
4. Calculate the mass percent of H2O:
- Mass percent of H2O = (mass of H2O / total mass of the hydrate) * 100
Now, let's perform the calculations:
- Molar mass of Cr(NO3)3 = 51.996 g/mol
- Molar mass of 9H2O = 162.216 g/mol
- Total molar mass of the hydrate = 51.996 g/mol + 162.216 g/mol = 214.212 g/mol
- Mass of H2O = 162.216 g/mol / 214.212 g/mol = 0.757 g
- Mass percent of H2O = (0.757 g / total mass of the hydrate) * 100
To calculate the mass percent to 3 significant figures, you need the total mass of the hydrate. Assuming you have that value, plug it into the formula above and round the result to 3 significant figures.
It depends if you are determining from mass measurements, or a formula calculation.
I assume you took an experment, measured some of the hydrate, heated it, then measured the unhydrated salt.
In that case,
Percenthydrate= 100* (masshydrate-massunhydrated)/masshydrated
Now, to do this to three sig figures might be a problem, as the number of sig digits might be determined by the subtracation, rather than your wishes.
For instance, say
mass hydrated= 10.34 grams
mass unhydrage= 9.51 grams
subtracting, one gets .83 grams, and you cannot get three sig figures from this.