1. Briefly, explain how the following procedural errors would affect the calcula
ID: 1058328 • Letter: 1
Question
1. Briefly, explain how the following procedural errors would affect the calculated mass percent of NaHCO3 in an NaHCO3 -NaCl mixture.
(a). A student, rushing to complete the mixture analysis, continued to strongly heat her sample after its melted.
(b). A student failed to store the cool crucible in a desiccator, allowing the crucible and contents to cool overnight on the laboratory bench
(c). Arriving late to class, a student had time to perform only one heating of the mixture.
(2).Calculate the mass loss on heating 1.200 g of NaHCO 3-NaCl mixture containing 65% NaCl.
(3). Limestone is a binary mixture of calcium and magnesium carbonates, CaCO3 and MgCO3. At 5000C, MgCO 3 thermally decomposes according to the reaction shown in equation below, while CaCO3 remains unchanged. MgCO3 thermally decomposes according to the reaction shown in equation below, while CaCO3 remains unchanged.
MgCO3(s) ---------- MgO(s) + CO2 (g)
When heated at 500 0C, a 2.000-g sample of limestone from a local quarry losses 0.273 g. Calculate the mass percent of MgCO3 present in the limestone.
Explanation / Answer
1(a). When a mixture is heated after it is melted, the mixture will start boiling and after a certain period, it will evaporate. As the mixture will evaporate and turns into gas, some mass of the mixture is lost. Hence, there will be some loss in mass of the mixture.
(b). Since the student failed to store the cool crucible in a desiccator, the crucible and contents will absorb moisture and hence there will be increase in mass.
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