A 0.972-g; CaCl 2 2H 2 C 4. sample of a / H2O solid salt mixture is dissolved in 150 of deionized water , previously adjusted to a pH that is basic . The precipitate , after having been filtered and air - dried , has a mass of 0.375 g . The limiting reactant in the salt mixture was later determined to be CaCl 2 2H 2 O a . What is the percent by mass of CaCl 2 2H 2 O in the salt mixture ?
To be honest the first sentence makes no sense whatsoever (what's a, what's /H2O, what's the salt mixture) so I'll assume that CaCl2.2H2O in a basic solution will ppt Ca(OH)2. Assuming that do this.
1. Convert 0.375 g Ca(OH2 to CaCl2.2H2O.
2. Solve for % CaCl2.2H2O in the sample.
Answers:
1. 0.375 g Ca(OH)2 x [molar mass CaCl2.2H2O/molar mass Ca(OH)2] = ?
2. %CaCl2.2H2O = (mass CaCl2.2H2O from #1/0.972)*100 = ?
Post your work if you get stuck. I may have not made the correct assumptions.
no tutor should have to assume what a student is asking.
and, students who can't put the correct word in the School Subject box probably aren't learning much English or science. how sad.
To find the percent by mass of CaCl2 2H2O in the salt mixture, we need to determine the moles of CaCl2 2H2O and the total moles of the salt mixture.
1. Determine the moles of CaCl2 2H2O:
- The molar mass of CaCl2 2H2O is calculated as follows:
- Molar mass of Ca = 40.08 g/mol
- Molar mass of Cl2 = 2 * 35.45 g/mol = 70.90 g/mol
- Molar mass of 2H2O = 2 * (2 * 1.01 g/mol + 16.00 g/mol) = 36.04 g/mol
- Therefore, the molar mass of CaCl2 2H2O = 40.08 g/mol + 70.90 g/mol + 36.04 g/mol = 146.02 g/mol
- We have a sample of 0.375 g of the precipitate. Let's convert this to moles:
- Moles of CaCl2 2H2O = mass / molar mass = 0.375 g / 146.02 g/mol = 0.002566 mol
2. Determine the total moles of the salt mixture:
- We know the mass of the CaCl2 2H2O + H2O mixture is 0.972 g.
- Let's subtract the mass of the precipitate to find the mass of the remaining H2O:
- Mass of H2O = Mass of mixture - Mass of precipitate = 0.972 g - 0.375 g = 0.597 g
- We can now calculate the moles of H2O:
- Moles of H2O = mass / molar mass = 0.597 g / 18.02 g/mol = 0.0331 mol
3. Calculate the moles of CaCl2 2H2O in the original mixture:
- Subtract the moles of H2O from the total moles of the mixture:
- Moles of CaCl2 2H2O = Total moles - Moles of H2O = 0.002566 mol - 0.0331 mol = -0.0305 mol
(Note: The negative sign indicates that there is not enough CaCl2 2H2O to fully react. It is the limiting reactant.)
4. Find the percent by mass of CaCl2 2H2O in the salt mixture:
- To do this, we need to determine the mass of the salt mixture.
- Mass of salt mixture = Mass of precipitate + Mass of H2O = 0.375 g + 0.597 g = 0.972 g
- Calculate the percent by mass of CaCl2 2H2O:
- Percent by mass of CaCl2 2H2O = (Moles of CaCl2 2H2O / Total moles) × 100
- Percent by mass of CaCl2 2H2O = (0.002566 mol / (0.002566 mol - 0.0331 mol)) × 100
- Percent by mass of CaCl2 2H2O ≈ 7.6% (rounded to one decimal place)
Therefore, the percent by mass of CaCl2 2H2O in the salt mixture is approximately 7.6%.
To determine the percent by mass of CaCl2 2H2O in the salt mixture, we need to calculate the moles of CaCl2 2H2O and the moles of the other component of the mixture. Then we can use the formula:
Percent by mass = (mass of CaCl2 2H2O / mass of salt mixture) * 100
Let's go step by step to solve this problem:
Step 1: Calculate the moles of CaCl2 2H2O
We need to convert the mass of CaCl2 2H2O to moles. The molar mass of CaCl2 2H2O is the sum of the molar masses of calcium chloride (CaCl2) and water (H2O). Use the atomic masses of each element:
The atomic masses are:
Ca = 40.08 g/mol
Cl = 35.45 g/mol
H = 1.008 g/mol
O = 16.00 g/mol
Molar mass of CaCl2 2H2O = (40.08 g/mol) + 2*(35.45 g/mol) + 2*(1.008 g/mol)+(16.00 g/mol) = 147.02 g/mol
Now we can calculate the moles of CaCl2 2H2O using the formula:
moles of CaCl2 2H2O = mass of CaCl2 2H2O / molar mass of CaCl2 2H2O
= 0.972 g / 147.02 g/mol
Step 2: Calculate the moles of the other component
To determine the moles of the other component, we need to subtract the moles of CaCl2 2H2O from the total moles of the salt mixture. We can assume that the mass of the other component is equal to the mass of the salt mixture minus the mass of CaCl2 2H2O precipitate.
mass of CaCl2 2H2O precipitate = 0.375 g
mass of salt mixture = 0.972 g
mass of the other component = mass of salt mixture - mass of CaCl2 2H2O precipitate
= 0.972 g - 0.375 g
Step 3: Calculate the moles of the other component
Now we can calculate the moles of the other component using its mass and molar mass. Let's assume the other component is X.
moles of X = mass of X / molar mas of X
Step 4: Calculate the percent by mass of CaCl2 2H2O in the salt mixture
Finally, we can calculate the percent by mass of CaCl2 2H2O in the salt mixture using the formula:
percent by mass = (moles of CaCl2 2H2O / total moles of the salt mixture) * 100
Now you can substitute the values from the previous steps into the equation and calculate the final answer.