8.00 g of calcium chloride, CaCl2, is dissolved in 1.000 Kg of water.
Molecular weights, Ca= 40 g/ mol, Cl= 35.5 g/ mol, H= 1 g/mol, O= 16 g/ mol
Density = 1 g/cm3
a. How many moles of CaCl2 are in solution?
b. How many moles of water are present?
c. Find the number of H atoms in water molecules.
d. Assume that the ionic compound, CaCl2, separates completely into Ca2+ and
Cl- ions when it dissolves in water. How many moles of each ion are present in
the solution?
a. How many moles of CaCl2 are in solution?
moles = grams/molar mass = ?
b. How many moles of water are present?
moles = grams/molar mass = ?
c. Find the number of H atoms in water molecules.
# H atoms = moles H2O x 2 x 6.02E23 = ?
d. Assume that the ionic compound, CaCl2, separates completely into Ca2+ and
Cl- ions when it dissolves in water. How many moles of each ion are present in
the solution?
moles Ca^2+ = moles CaCl2
moles Cl^- = moles CaCl2 x 2 = ?
a. Well, if we want to figure out how many moles of CaCl2 are in solution, we need to do a little math dance. Let's start by finding the molar mass of CaCl2: Ca (40 g/mol) + 2 Cl (35.5 g/mol) = 110 g/mol.
Now, we can use the formula n = m/M, where n is the number of moles, m is the mass, and M is the molar mass.
Plugging in the values, we have n = 8.00 g / 110 g/mol = 0.0727 moles of CaCl2.
b. To determine how many moles of water are present, we need to use the same formula. The molar mass of water is H2O, which is 1 g/mol (for 2 H atoms) + 16 g/mol (for 1 O atom) = 18 g/mol.
Using n = m/M, we have n = 1000 g / 18 g/mol ≈ 55.6 moles of water.
c. Ah, the good ol' H atoms in water molecules. Well, in one molecule of water, there are 2 H atoms. Since we have approximately 55.6 moles of water, we can multiply that by Avogadro's number (6.022 x 10^23) to find the total number of H atoms.
So, 55.6 moles of water x 2 H atoms/molecule x 6.022 x 10^23 molecules/mole = a large number of H atoms! (approximately 6.7 x 10^25)
d. Let's tackle the ions. Since CaCl2 separates into Ca2+ and 2 Cl- ions, we need to multiply the number of moles of CaCl2 by the appropriate coefficient.
We found earlier that there are 0.0727 moles of CaCl2, so we have:
0.0727 moles of CaCl2 x 1 mole of Ca2+ / 1 mole of CaCl2 = 0.0727 moles of Ca2+.
And 0.0727 moles of CaCl2 x 2 moles of Cl- / 1 mole of CaCl2 = 0.145 moles of Cl-.
There you have it! The solution is finding the answers to these questions and a sprinkle of chemistry humor.
a. To find the number of moles of CaCl2 in solution, we need to divide the mass of CaCl2 by its molecular weight.
Molecular weight of CaCl2 = (1 * 40) + (2 * 35.5) = 40 + 71 = 111 g/mol
Number of moles of CaCl2 = Mass of CaCl2 / Molecular weight of CaCl2
= 8.00 g / 111 g/mol
b. To find the number of moles of water present, we need to divide the mass of water by its molecular weight.
Molecular weight of water = 2(1 * H) + 16 = 2 + 16 = 18 g/mol
Number of moles of water = Mass of water / Molecular weight of water
= 1.000 Kg * 1000 g/Kg / 18 g/mol
c. Each molecule of water, H2O, consists of 2 hydrogen (H) atoms. So, the number of H atoms in water molecules is 2 times the number of moles of water found in part b.
Number of H atoms in water molecules = 2 * Number of moles of water
d. Since the ionic compound CaCl2 separates completely into Ca2+ and Cl- ions when it dissolves in water, the number of moles of each ion will be equal to the number of moles of CaCl2 found in part a.
Number of moles of Ca2+ ions = Number of moles of Cl- ions = Number of moles of CaCl2
To find the answers to these questions, we need to use some basic principles of chemistry, such as the molar mass, stoichiometry, and Avogadro's number.
a. To determine the number of moles of CaCl2 in the solution, we can use the formula:
moles = mass / molar mass
Given that the mass of CaCl2 is 8.00 g and the molar mass of CaCl2 is 40.08 g/mol (calcium has a molar mass of 40.08 g/mol, and chlorine has a molar mass of 35.5 g/mol), we can substitute these values into the formula:
moles = 8.00 g / 40.08 g/mol ≈ 0.199 moles
Therefore, there are approximately 0.199 moles of CaCl2 in the solution.
b. The number of moles of water can be calculated using the same formula:
moles = mass / molar mass
Given that the mass of water is 1.000 Kg and the molar mass of water is 18.02 g/mol (hydrogen has a molar mass of 1 g/mol, and oxygen has a molar mass of 16 g/mol), we need to convert the mass of water to grams before substituting values into the formula:
1.000 Kg = 1000 g
moles = 1000 g / 18.02 g/mol ≈ 55.49 moles
Therefore, there are approximately 55.49 moles of water present.
c. To find the number of H atoms in water molecules, we need to consider the molecular formula of water, H2O.
In one molecule of water, there are 2 hydrogen atoms (H2) and 1 oxygen atom (O). Therefore, the number of H atoms in water molecules is 2.
d. If we assume that the ionic compound CaCl2 separates completely into Ca2+ and Cl- ions when it dissolves in water, we can determine the number of moles of each ion present in the solution.
Since each CaCl2 molecule generates one Ca2+ ion and two Cl- ions, the number of moles of Ca2+ ions will be the same as the number of moles of CaCl2, which is approximately 0.199 moles.
As each CaCl2 molecule generates two Cl- ions, the number of moles of Cl- ions will be double the number of moles of Ca2+ ions, which is approximately 0.398 moles.
Therefore, there are approximately 0.199 moles of Ca2+ ions and 0.398 moles of Cl- ions present in the solution.