HELP ASAP if you're good at gen chem I /AP chem: A student wishes to prepare a solution with a final concentration of Na+ = 0.50 M and a final concentration of HCO3– = 0.10 M by taking some NaOH and some trona (Na2CO3•NaHCO3•2H2O) and diluting with water to a final volume of 1.00 L. How much NaOH and trona are required? the answer is 0.05 mol NaOH and 0.15 mol trona, but I just don't understand how in the world to get there!?

Moles of trona are 0.15moles

Moles of NaOH are 0.05mol

Explanation:

In the problem, you have 2 solutes, NaOH and trona.

Based in its formula, in solution, 1 mole of NaOH will produce 1 mole of Na⁺ and 1 mole of trona will produce 3 moles of Na⁺ and 1 mole of HCO₃⁻.

Also, you must know HCO₃⁻ will react with NaOH producing CO₃²⁻.

You want 1L of 0.50M Na⁺ = 0.50 moles of Na⁺ and 1L of HCO₃⁻ = 0.10M.

Now, in equations, moles of Na⁺ will be:

Moles Na⁺ = 0.50moles = X + 3Y (1)

Where X are moles of NaOH and Y moles of trona.

And, moles of HCO₃⁻ will be:

Moles HCO₃⁻ = 0.10moles = Y - X (2)

The sum of (1) + (2):

0.60mol = 4Y

0.15mol = Y

And moles of NaOH are (Replacing in (1) or (2) you will obtain the same, I will replace in (1)) :

0.50moles = X + 3Y

0.50moles = X + 3×0.15mol

0.50moles = X + 0.45mol

0.05 moles = X

vanderwaal's forces of attraction are the electrostatic intermolecular forces that exist in a molecule due to the temporary or permanent dipoles that are developed in a molecule. in , the major intermolecular forces are dipole-dipole interactions as the molecule is polar (bent structure). so the vanderwaal's forces of interaction in between molecules are the permanent dipole-dipole interactions that develop due to the dipole that exists in between the polar h - s bond. the positively charged hydrogen atom is attracted towards the negative end of the dipole that is sulfur of the adjacent molecule. therefore, these forces of attraction are relatively stronger than that of london dispersion forces that exist in non polar molecules.