What mass in grams of a 0.500 m(molal) solution of sodium acetate, CH3CO2Na, in water would you use to obtain 0.200mol of sodium acetate?

416 grams

0.200 mol ch3coona are in 1041/0.5×0.200

= 416.4g solutiob

To find the mass of sodium acetate needed to obtain 0.200 mol, we need to follow a few steps:

Step 1: Understand the concept of molality (m):

Molality (m) is defined as the number of moles of solute (in this case, sodium acetate) per kilogram of solvent (in this case, water). It is usually represented as "mol/kg".

Step 2: Determine the molality (m) of the solution:

Given: Molality (m) = 0.500 mol/kg

This means that for every kilogram of water, we have 0.500 moles of sodium acetate dissolved in it.

Step 3: Determine the number of moles of sodium acetate needed:

Given: Number of moles of sodium acetate (n) = 0.200 mol

Step 4: Calculate the mass of sodium acetate:

To calculate the mass, we can use the formula:

mass = molality (m) x molecular weight (MW) x mass of solvent (kg)

First, we need to find the molecular weight (MW) of sodium acetate, which is the sum of the atomic weights of each atom in the formula CH3CO2Na:

C: 1 atom x 12 g/mol = 12 g/mol
H: 3 atoms x 1 g/mol = 3 g/mol
O: 2 atoms x 16 g/mol = 32 g/mol
Na: 1 atom x 23 g/mol = 23 g/mol

MW of sodium acetate = 12 + 3 + 32 + 23 = 70 g/mol

Now, we can use the formula to find the mass:

mass = 0.500 mol/kg x 70 g/mol x mass of solvent (kg)

We need to find the mass of sodium acetate in grams, so we assume 1 kg of water (as molality is defined per kilogram) is used:

mass = 0.500 mol/kg x 70 g/mol x 1 kg = 35 g

Therefore, you would need 35 grams of a 0.500 m(molal) solution of sodium acetate in water to obtain 0.200 mol of sodium acetate.

0.5 m solution = 0.5 mol solute/kg solvent.

mol = g/molar mass and molar mass = about 82 g/mol.
0.5 mol = 1/2*82 = about 41
So 41g CH3COONa in 1 kg H2O = total mass of 1041g.

You want 0.2 mol CH3COONa so
1041g x (0.2/0.5) = ? mass solution