composition of a hydrate Answer 1-4 please In this experiment you are to remove
ID: 890615 • Letter: C
Question
composition of a hydrate Answer 1-4 please In this experiment you are to remove the water of hydration by heating. Why do you have to heat it at least twice instead of heating the hydrate just once for a prolonged period of time? If you neglected to heat the hydrate gently the first time and splattering occurs, how would it affect your percent of water of hydration? Be specific. Predict whether it would be too high or too low and explain your answer. A student, John, reported the following for his unknown hydrate: We know there is something wrong with his reported values even without knowing the formula of his anhydride. What type of error would cause this? Explain fully. A student, Mary, used 1.2 g of hydrate in the first trial and 1.6 g in the second trial. Explain fully why her mass percent of water will be the same for both trials even though she used more hydrate in the second trial. (Do not simply state that the mass percent is an intensive property.)Explanation / Answer
1) The sample contains water in two forms one is the moisture and the other is the water of hydration. Moisture is loosely held whereas the water of hydration is strongly held. First the sample is gently heated so that the moisture is removed. Then the sample is strongly heated so that the water of hydration is removed.
2) If first time, gentle heating is not provided, and splatering occurs, the loss in mass will be higher than the expected value. Hence, the water of hydration calculated will be more than the actual value. It will be two high.
3) The percent water is around 36 %. This is two high value. This indicates that during heating, some splattering has happened.
4) The mass percent of water will be same for both the trials because the mass percent represents the mass of water present in 100 g of sample. It is a ratio of two quantities and is independant of the actual mass taken for the trail.
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