Pre Lab and Post Lab Questions – Flashcards
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List some physical properties that can be used to identify unknown substances
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1. Solubility 2. Density 3. Melting Point 4. Boiling Point
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The freezing point is the equilibrium temperature when solid begins to appear in the ____ phase
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Liquid
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The normal boiling point is the temperature at which a liquid boils at ____ mmhg
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760
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The volume of a solid can be measured in a solvent in which the solute is
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Insoluble
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Cadmium nitrate is soluble in water and insoluble in cyclohexane. Which solvent will be used to measure the volume of Cadmium nitrate?
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Cyclohexane
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Is thymol a solid or liquid at room temperature?
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Solid
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What solvent would you use to measure the density of magnesium nitrate?
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Cyclohexane
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If air bubbles were trapped in your solid beneath the liquid level in your density determination, what error would result in the volume measurement, and what would be the effect of this error on the calculated density?
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The volume would be more than what it should actually be and it would cause the density calculation to be too small
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A liquid was found to be insoluble in water and soluble in cyclohexane and alcohol; the unknown was found to have a boiling point of 107°C at 658 mmHg. What is the substance?
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Toluene
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A liquid has a density of 0.80±0.01 g/mL is insoluble in cyclohexane. What is the liquid?
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Propionaldehyde
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What is the boiling point of cyclohexane at 600 mm Hg? Calculate
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75.5°C
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Osmium is the densest element known. What are its density and melting point?
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Melting Point=3,027°C Density=22.59 g/cm³
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What is the color of MnSO?? What is its solubility in cold water?
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-A light pink -Highly soluble in cold water
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What is the formula, molecular weight, and color of lead azide?
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-Formula= Pb(N?)? -Molecular Weight=291.24g/mol -Color=White
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Define the process of sublimation
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Process in which a solid will go to the gaseous state, and from a gas to a solid without being in a liquid state
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Why does one never weigh a hot object?
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Because the weight would not be accurate, The substance will emit energy because it would be in constant motion, thus throwing off the weight of the measurement.
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What is the principle of the conservation of matter?
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Matter cannot be created or destroyed
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How could you serparate barium sulfate, BaSO?, from NH?Cl
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Heat the ammonium chlorate to the sublimation point at 1580°C, then barrium sulfate is then going to to melt
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How could you separate zinc chloride, ZnCl?, from zinc sulfide, ZnS?
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Zinc chloride will melt down then it would have to be filtered because zinc sulfide is still a solid
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How could you separate tellurium dioxide, TeO?, from SiO??
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TeO? is not soluable in HF, therefore we would use SiO? because it is soluable
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Naphthalene sublimes easily but potassium bromide does not. How could you separate these two substances?
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Heat up the napthalene and potassium bromide until you only have potassium bromide since naphthalene is sublime
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What is the difference between an empirical formula and a molecular formula?
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The empirical formula uses the simplest atomic ratio between the element in the compound. The molecular formula is a multiple of the empirical formula.
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A compound contains 0.0130 mol carbon, 0.0390 mol hydrogen, and 0.0065 mol oxygen. Determine the empirical formula.
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C?H?O
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When 6.25g of pure iron reacts with oxygen, it produces a product of 8.15g. What is the empirical formula of the product?
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FeO
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What does quantitative and qualitative mean?
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-Quantitative is how much of one more more chemicals are in a sample -Qualitative deals with descriptions/can be observed
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What does gravimetric analysis mean?
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It will determine the amount of a constituent by isolating it in a weighable form.
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Why is it important to determine the standard deviation?
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To estimate the precision
