Multiple Choice
How many moles of oxygen atoms are present in 25.45 g of CaCO₃?
2. Atoms & Elements
Mole Concept
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What is the total concentration of ions in a 0.0360 M solution of Na₂CO₃?
A
0.1440 M
B
0.0720 M
C
0.1080 M
D
0.0360 M
Verified step by step guidance1
Identify the chemical formula of sodium carbonate, which is Na₂CO₃. This compound dissociates in water to form ions.
Write the dissociation equation for Na₂CO₃: Na₂CO₃ → 2 Na⁺ + CO₃²⁻. This shows that each formula unit of Na₂CO₃ produces two sodium ions (Na⁺) and one carbonate ion (CO₃²⁻).
Determine the concentration of each ion produced from the dissociation. Since the initial concentration of Na₂CO₃ is 0.0360 M, the concentration of Na⁺ ions will be twice that, due to the stoichiometry of the dissociation equation: 2 × 0.0360 M = 0.0720 M.
Calculate the concentration of CO₃²⁻ ions, which is equal to the initial concentration of Na₂CO₃, 0.0360 M, because one CO₃²⁻ ion is produced per formula unit of Na₂CO₃.
Add the concentrations of all ions to find the total concentration of ions in the solution: 0.0720 M (Na⁺) + 0.0360 M (CO₃²⁻) = 0.1080 M.
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