A 25 g sample of a hydrate of Ca(NO3)2 was heated, and only 1.7 g of the anhydrous salt remained. What hydrate of Ca(NO3)2 was tested?
Water in the sample = 25 g - 1.7 = 23.3
mols salt = 1.7/164 = approx 0.0104
mol H2O = 23.3/18 = 1.29
Find the ratio:
0.0104/0.0104 = 1.00
1.29/0.0104 = 124
So the formula would be Ca(NO3)2*124H2O but I don't believe this. Better check your numbers.
To determine the hydrate of Ca(NO3)2 that was tested, we can calculate the mass of water that was lost during heating.
Given:
Mass of the original sample (hydrate) = 25 g
Mass of the anhydrous salt remaining = 1.7 g
Step 1: Calculate the mass of water lost
Mass of water lost = Mass of the original sample - Mass of the anhydrous salt remaining
Mass of water lost = 25 g - 1.7 g
Mass of water lost = 23.3 g
Step 2: Calculate the molar mass of water (H2O)
The molar mass of water (H2O) = 2 * atomic mass of hydrogen + 1 * atomic mass of oxygen
The atomic mass of hydrogen (H) = 1 g/mol
The atomic mass of oxygen (O) = 16 g/mol
Molar mass of water (H2O) = 2 * 1 g/mol + 1 * 16 g/mol
Molar mass of water (H2O) = 18 g/mol
Step 3: Calculate the number of moles of water lost
Number of moles of water lost = Mass of water lost / Molar mass of water
Number of moles of water lost = 23.3 g / 18 g/mol
Number of moles of water lost ≈ 1.294 moles
Step 4: Determine the ratio of water to anhydrous salt (Ca(NO3)2)
From the formula of Ca(NO3)2, we can see that there are 2 nitrate ions (NO3-) for every 1 calcium ion (Ca^2+). Since there are no water molecules in the anhydrous salt, there must have been water molecules associated with each calcium nitrate unit in the hydrate compound.
So, the ratio of water to anhydrous salt = 1.294 moles of water lost / 1.7 g of anhydrous salt remaining
Step 5: Determine the formula of the hydrate
To determine the formula of the hydrate, we need to find the ratio of water molecules per mole of anhydrous salt. Since the molar mass of the anhydrous salt Ca(NO3)2 is approximately 164 g/mol, we can calculate the number of moles of anhydrous salt remaining.
Number of moles of anhydrous salt = Mass of anhydrous salt remaining / Molar mass of anhydrous salt
Number of moles of anhydrous salt = 1.7 g / 164 g/mol
Number of moles of anhydrous salt ≈ 0.010 moles
Therefore, the hydrate of Ca(NO3)2 that was tested was Ca(NO3)2·10H2O (Calcium nitrate decahydrate).
To determine the hydrate of Ca(NO3)2 that was tested, we need to calculate the amount of water lost during the heating process.
Let's start by finding the amount of water in the hydrate before heating.
Given:
Initial mass of the hydrate (before heating) = 25 g
Mass of the anhydrous salt (after heating) = 1.7 g
The mass of water lost during heating is calculated by subtracting the mass of the anhydrous salt from the initial mass of the hydrate:
Mass of water lost = Initial mass of the hydrate - Mass of the anhydrous salt
= 25 g - 1.7 g
= 23.3 g
Since water has a molar mass of approximately 18 g/mol, we can calculate the number of moles of water lost:
Number of moles of water lost = Mass of water lost / molar mass of water
= 23.3 g / 18 g/mol
≈ 1.295 mol
Now, let's calculate the number of moles of Ca(NO3)2 in the anhydrous salt that remained:
Number of moles of Ca(NO3)2 = Mass of anhydrous salt / molar mass of Ca(NO3)2
Given that the molar mass of Ca(NO3)2 is approximately 164 g/mol and the mass of the anhydrous salt is 1.7 g:
Number of moles of Ca(NO3)2 = 1.7 g / 164 g/mol
≈ 0.0104 mol
By comparing the mole ratios of water to Ca(NO3)2, we can determine the formula of the hydrate. In this case, the ratio is approximately 1.295 mol of water to 0.0104 mol of Ca(NO3)2.
The simplified mole ratio is approximately 124:1. This indicates that for every 124 moles of water, there is 1 mole of Ca(NO3)2.
Based on this ratio, we can conclude that the hydrate of Ca(NO3)2 tested is Ca(NO3)2 · 124H2O.