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Answer:
[Na₂CO₃] = 0.15 M
Explanation:
Molarity is a type of concentration.
It is useful for solutions, to say how many moles of solute are contained in 1L of solution.
We can also say, that molarity are the mmoles of solute in 1 mL of solution.
In this case, our solute is the Na₂CO₃.
We convert mass to moles: 0.79 g . 1 mol / 106g = 7.45×10⁻³ moles
We convert moles to mmoles: 7.45×10⁻³ mol . 1000 mmol / 1mol = 7.45 mmol
M = mmol / mL
M = 7.45 mmol / 50 mL = 0.15 M
Option A is the right answer.