1. Part A.1. The crucible is not fired, as the procedure suggests, but had retained some impurities from previous use (or it could only be oily smudges from fingers). The mass of the "dirty" crucible is recorded. However the impurities are burned off in the experiment. Will the reported mass of the final product be too high, too low, or unchanged as a result of this technique error? Explain.
If there is dirt left over on the crucible from the last experiment, it has retained some impurities from this previous use. The “dirty” pass is recorded, and the impurities are burned off. The mass of the final product will be too high do to not firing off the impurities before weighing.
2. Part B.1. Javier forgot to polish the magnesium metal. Will the reported mole ratio of magnesium to oxygen be too high or too low as a result of his error? Explain?
The mld ratio of magnesium to oxygen would be too low. The magnesium unpolished is actually covered in a protective layer of Oxygen, being MgO, so its heavier. The calculated mole value would be higher. A bigger denominator the O2/Mg ratio will give smaller ratio.
Part B.2. The burning of the magnesium becomes uncontrolled (it burns brightly). Will the reported mole ration of magnesium to oxygen be too high or too low as a result of this technique error? Explain.
Less oxidation will occur while its burning, so the ratio to O2 to magnesium would be much higher than usual.
Part. B.3. In a Hurry to complete the experiment, Josh did not allow all of the magnesium to react. Will his reported magnesium to oxygen ration be reported too high or too low? Explain.
If not all of the magnesium is reacted and oxidized, there will be more magnesium present in the end result, then the Mg:O ratio will be too high. His reported ratio will be too high.
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This book can be very vague and I am a novice when it comes to chemistry so please, again, correct me where I've gone wrong.