Thank you for the opportunity to help you with your question!

what is the osmolaritry of a o.3M solution of NaCl?

NaCl) dissociates into Na^{+} and Cl^{−} ions. Thus, for every 1 mole of NaCl in solution, there are 2 osmoles of solute particles (i.e., a 1 mol/L NaCl solution is a 2 osmol/L NaCl solution

thus osmolarity will be 0/6 osmol/L

How many grams of MgSO4 are needed to prepare a 1M MgSO4 solution?

1 M MEANS 1MOLE per litre of solution

molar mass = 120.37

mass in gramss = moles* molar mass

= 1* 120.37 = 120.37grams

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