Chemlab 2 - Lecture notes 4-7 PDF

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Prof. Spielholtz...

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Chemistry Pre-Lab Questions September 14, 2014 Prof. Spielholtz Experiment 2

1. Classify each of the following as a pure substance or a mixture. If a mixture, state whether its heterogeneous or homogenous. a) concrete: pure substance b) tomato juice mixture heterogeneous c) marble: pure substance d) seawater: mixture homogenous e) iron: Pure substance

2. A suggested way is to measure the boiling points of water and salt solution. The salt solution should have a greater boiling point than pure water and that is how you can determine the liquid. 3. If there is one component in a substance, it is an impure substance and if there are two components , then it is a mixture. 4. Sublimation: the process in which a substance becomes a solid from the gaseous state without passing through liquid phase. 5. Decantation i sapr oc essf ort hesepar at i onofmi xt ur es butfil t r at i oni st hepr ocessi ns epar at i ngs ol i ds f r om l i qui dsbyusi ngafil t erwher el i qui dssepar at ef r om t hecont ai nerandt hesol i dsr emai n.Fi l t r at i on pr oducesc l ear erfil t r at ebuti tt ak esl ongert odo.Ther ef or e,decant at i oni sf ast er . 6.Ahotobj ectcandamageabal anc e;t her ef or e,i ts houl dbecool eddownbef or ebei ngwei ghed.The obj ectr adi at esener gyi nt hef or m ofheat . 7.Thes um oft hewei ght soft hec omponent ss houl dbeequal t ot hewei ghtoft hesampl e.Nomat t eri s bei ngconv er t edi nt oener gyi nt hi sex per i ment . 8.1. 05g +0. 69g+2. 17g=3. 91g

1. 05g/3. 91gx100 =27% SiO₂

9. Zinc chloride is insoluble in cyclohexane and cannot be separated by filtration. 10. Zinc chloride is soluble in water so you when you mix them , zinc chloride will dissolve and SiO₂ will too. Then, when they are heating, using filtration, they will separate. 11. The student did not make accurate measurements. They must be precise and it is clear that her measurements were higher than they should have been. 12. NaCl is extracted more than one time to make sure that all the NaCl is taken out. This is done three times to make sure there is no more NaCl left....