A #20*g# mass of #CaCl_2# was dissolved in #700*g# of water. What is the molality of the solution with respect to #"calcium chloride"#?

Question

A #20*g# mass of #CaCl_2# was dissolved in #700*g# of water.  What is the molality of the solution with respect to #"calcium chloride"#?

Olivia Anton · Accepted Answer

#"Concentration"-=0.257*"molal"#.........

#"Molality"# #-=# #"Moles of solute"/"Kilograms of solvent"# Consequently,... The formula for "molality" is ((20*g)/(110.98*g*mol^-1))/(700*gxx10^-3*kg*g^-1) = 0.257*mol*kg). Note that at (relatively!) low concentrations, the calculated #"molality"# would be almost the same as solution #"molarity"#. #"Molality"# is used because the expression is fairly independent of temperature. What is the #"molal concentration"# with respect to #"chloride ion"#?

Wyatt Atkins · Answer

#0.25# #molal# Chemical formula of Calcium chloride= #CaCl_2# Molar mass of #CaCl_2# =#110.98# #gmol^-1# Mass of Calcium chloride (given) = #20g# #Molality# = #m# = #("moles of solute")/"kg of solvent"# Now, to calculate no. of moles: No. of moles = #("mass")/"molar mass"# No. of moles= #("20g")/"110.98g/mol"# = #0.180# moles #g# of solvent = # 700 g # Converting #g# #-># #kg# #kg# of solvent = #0.7kg# Water is solvent while #CaCl_2# is solute Now, #Molality# = #m# = #("moles of solute")/"kg of solvent"# #Molality# = #("0.180 moles")/"0.7kg"# #Molality# = #0.25# # molal#

Cooper Anderson · Answer

undefined To find the molality of the solution with respect to calcium chloride, you need to first calculate the number of moles of calcium chloride dissolved in the water.

1. Calculate the number of moles of CaCl2:
   Mass of CaCl2 = 20 g
   Molar mass of CaCl2 = 40.08 g/mol (for Ca) + 2 * 35.45 g/mol (for Cl) = 110.98 g/mol
   Number of moles of CaCl2 = Mass / Molar mass = 20 g / 110.98 g/mol ≈ 0.1803 moles

2. Calculate the molality of the solution:
   Molality (m) = moles of solute / mass of solvent in kg
   Mass of solvent (water) = 700 g = 0.700 kg
   Molality of CaCl2 = 0.1803 moles / 0.700 kg ≈ 0.2576 mol/kg

So, the molality of the solution with respect to calcium chloride is approximately 0.2576 mol/kg.

Naomi Aronson · Answer

undefined To find the molality of the solution with respect to calcium chloride, use the formula:

$$ \text{Molality} = \frac{\text{Number of moles of solute}}{\text{Mass of solvent in kilograms}} $$

First, calculate the number of moles of calcium chloride (CaCl2). To do this, you need to know the molar mass of CaCl2, which is the sum of the atomic masses of calcium (Ca) and two chlorine (Cl) atoms.

The atomic mass of calcium (Ca) is approximately 40.08 g/mol, and the atomic mass of chlorine (Cl) is approximately 35.45 g/mol. Therefore, the molar mass of CaCl2 is:

$$ 1 \times \text{Ca} + 2 \times \text{Cl} = 40.08 + 2 \times 35.45 = 40.08 + 70.90 = 110.98 \, \text{g/mol} $$

Now, calculate the number of moles of CaCl2 using its molar mass and mass:

$$ \text{Number of moles of CaCl}_2 = \frac{\text{mass of CaCl}_2}{\text{molar mass of CaCl}_2} $$
$$ \text{Number of moles of CaCl}_2 = \frac{20 \, \text{g}}{110.98 \, \text{g/mol}} $$

Now, calculate the mass of the solvent (water) in kilograms:

$$ \text{Mass of solvent (water)} = \frac{700 \, \text{g}}{1000} = 0.7 \, \text{kg} $$

Finally, use the formula for molality:

$$ \text{Molality} = \frac{\text{Number of moles of solute}}{\text{Mass of solvent in kilograms}} $$
$$ \text{Molality} = \frac{20 \, \text{g} / 110.98 \, \text{g/mol}}{0.7 \, \text{kg}} $$

$$ \text{Molality} \approx \frac{0.1799 \, \text{mol}}{0.7 \, \text{kg}} $$

$$ \text{Molality} \approx 0.257 \, \text{mol/kg} $$

So, the molality of the solution with respect to calcium chloride is approximately $0.257 \, \text{mol/kg}$.