PHR2021: Workshop 2

Workshop 2 Calculations

  • Osmolarity concerns number of molecules in solution

  • Equivalents concerns charge of ions in solution

PHR2021: Workshop 2

Exercise 3: Osmolarity with dissoc. ratios

Moles of :

Since dissociates as follows:

Then,

PHR2021: Workshop 2

For KCl:

We know , so:

In total,

PHR2021: Workshop 2

Exercise 4: Osmolarity

  1. of each salt:

  1. Moles of each salt:

, so:

PHR2021: Workshop 2

, so:

In total,

PHR2021: Workshop 2

Exercise 5: Equivalents (Charge of ion)

200 mL of soln, 5 mEq of per 5mL is equivalent to:

Thus, the total mEq in 200 mL is:

PHR2021: Workshop 2

has a valency of 2, so:

Because we have the hydrated salt, which dissociates as follows:

Each mole of gives 1 mole of ,

so .

PHR2021: Workshop 2

Knowing we need 0.100 mol of , and its MW is 147 g/mol, we can calculate the mass:

What is the number of milliosmoles contained in the following solution? - $\mathrm{MgCl_2\cdot6H_2O}$ (MW = 203.3): 3.7 g - $\mathrm{KCl}$ (MW = 74.6): 3.0 g - Water for injections, to 100 mL -

Calculate the number of milliosmoles (mOsm) in the following solution: - 50 mL of 0.067 M $\mathrm{KH_2PO_4}$ (0.908\% w/v) (MW = 136) - 50 mL of 0.067 M $\mathrm{Na_2HPO_4\cdot12H_2O}$ (2.39\% w/v) (MW = 358)