G2 Mass, Moles and Direct Calculations Practice

Choose and rearrange the mass–amount relationship, keeping the units and magnitude consistent.

SEC G2 Science Chemistry component 2027

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Use Aᵣ(Na)=23, Aᵣ(C)=12, Aᵣ(O)=16, Aᵣ(Ca)=40, Aᵣ(Mg)=24 and Aᵣ(Cl)=35.5. Find the amount in 10.6 g of Na₂CO₃ and the mass of 0.250 mol of CaCO₃. In a separate calculation, a learner writes: Line 1, M(MgCl₂) = 24 + 35.5 = 59.5 g/mol; Line 2, n = 7.60/59.5 mol. Identify the first error and correct the molar mass and amount for that sample.

(a) Molar mass of Na₂CO₃, with units: Include g/mol.
(b) Relationship for amount from mass
(c) Amount in 10.6 g Na₂CO₃, with units: Include mol.
(d) Mass of 0.250 mol CaCO₃, with units: Include g.
(e) First error in the magnesium chloride calculation
(f) Correct molar mass of MgCl₂, with units: Include g/mol.
(g) Correct amount in 7.60 g MgCl₂, with units: Include mol.
(h) Effect of the learner's underestimated molar mass

G2 Mass, Moles and Direct Calculations Practice

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