If 10.0g of CaCl2 and 10.0g of NaCl are dissolved in 100.0mL of solution, what is the concentration of chloride ions? (the molar mass of CaCl2 is 111.0g/mol; the molar mass of NaCl is 58.44g/mol.
I found individual molar mass of:
Ca-40.08
Cl-35.45
Na-22.99
So I divided 10g CaCl2/111.0g CaCl2 + 10g NaCl/58.44g NaCl = .262205764. I than divided by .100L = 2.61205764.
I than divided 70.9g/111.0g and 35.45g/58.44g, added them together and came up with 1.245305065.
The final answer is 3.51M.
I cannot figure out where this answer came from. Help please.
I expect if I look really hard I could find exactly where you went off track but it is easier to show you how to do the problem.
Plan: Determine molarity CaCl2 and molarity NaCl, then multiply M CaCl2 by 2 (to find M Cl) and add to molarity NaCl.
mols CaCl2 = 10/111 = 0.09
M = moles/L = 0.09/0.1 = 0.9 M CaCl2
M Cl in CaCl2 is 2 x 0.9 = 1.8
moles NaCl = 10/58.44 = 0.171
M = moles/L = 0.171/0.1 = 1.71 M NaCl.
then 1.8 + 1.71 = 3.51 M to three s.f.
To find the concentration of chloride ions, you need to calculate the moles of chloride ions present in the solution. Let's go step by step:
1. Calculate the moles of CaCl2:
Given that you have 10.0g of CaCl2 and its molar mass is 111.0g/mol, you can use the formula:
moles of CaCl2 = mass of CaCl2 / molar mass of CaCl2
= 10.0g / 111.0g/mol
= 0.09 mol (rounded to two decimal places)
2. Calculate the moles of NaCl:
Given that you have 10.0g of NaCl and its molar mass is 58.44g/mol, you can use the formula:
moles of NaCl = mass of NaCl / molar mass of NaCl
= 10.0g / 58.44g/mol
= 0.17 mol (rounded to two decimal places)
3. Add the moles of chloride ions:
Since calcium chloride (CaCl2) dissociates into two chloride ions (Cl-), you need to multiply the moles of CaCl2 by 2:
moles of chloride ions from CaCl2 = 0.09 mol x 2 = 0.18 mol
The moles of chloride ions from NaCl remain the same, which is 0.17 mol.
4. Calculate the total moles of chloride ions:
To find the total moles of chloride ions, add the moles obtained from CaCl2 and NaCl:
total moles of chloride ions = moles of chloride ions from CaCl2 + moles of chloride ions from NaCl
= 0.18 mol + 0.17 mol
= 0.35 mol (rounded to two decimal places)
5. Calculate the concentration of chloride ions:
The concentration of chloride ions is expressed in moles per liter (M). Given that you have a total volume of 100.0 mL, you need to convert this to liters:
volume of solution in liters = 100.0 mL / 1000 mL/L
= 0.100 L (rounded to three decimal places)
Finally, divide the moles of chloride ions by the volume of the solution:
concentration of chloride ions = total moles of chloride ions / volume of solution
= 0.35 mol / 0.100 L
= 3.5 M (rounded to two decimal places)
Therefore, the concentration of chloride ions is 3.5 M.