101pex1sol - Chemistry 101 - Su08 Solutions for Practice...

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Chemistry 101 - Su08 Solutions for Practice Midterm 1 1) The symbols for silicon, arsenic, bromine, barium and cobalt are: Si, As, Br, Ba, Co E 2) Mixtures must contain two or more different substances. These substances can be elements (atomic or molecular) or compounds . There are essentially two types of mixtures, homogeneous and heterogeneous. The substances in a mixture can be separated into pure substances by physical means. Homogeneous mixtures are uniform throughout and have the same physical and chemical properties throughout. These are often referred to as solutions . Heterogeneous mixtures have physical and chemical properties that are NOT uniform throughout the sample. Heterogeneous mixtures may contain elements and may contain three substances (at least 2 or more). Pure substances are not mixtures. They are elements or compounds . They can not be separated into simpler substances through physical means but can be chemically decomposed into simpler pure substances. A pure substance can contain more than one type of atom. Table salt (NaCl) is a pure compound. Compounds are always composed of two or more different elements in fixed proportion by mass. If only one substance is present the material is a pure substance and the material must be uniform throughout (homogeneous). Both pure substances and solutions have properties that are uniform throughout. D 3) Sulfur (S), Xenon (Xe) and Phosphorus (P) are nonmetals. Lithium (Li) and Indium (In) are representative metals. Copper (Cu) and Platinum (Pt) are transition metals. Arsenic (As) and Antimony (Sb) are semimetals (metalloids). B (3 nonmetals and 2 semimetals)
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4) Physical properties of Sulfur: A. Its melting point is 112 °C B. It is a yellow solid D. Its density is 2.97 g/cm 3 Physical properties depend only on the substance itself and are properties that can be measured without changing the chemical identity of the substance. Chemical properties describe how a substance changes during a chemical reaction (i.e. How it reacts and what it reacts with.) E 5) The significant figures in a measured number include all the certain digits plus 1 extra digit (the last digit shown on the right) which is estimated. All non zero digits in a number are significant. Zeros in a quantity may or may not be significant. Leading zeros (zeros before first nonzero digit) are not significant (0.001 has 1 s.f.). Captive zeros (zeros between other nonzero numbers) are significant (1.001 has 4 s.f.). Trailing zeros are significant if they follow a nonzero digit to the right of the decimal point (1.10 has 3 s.f.).
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This note was uploaded on 07/17/2008 for the course CHEM 101 taught by Professor Stegemiller during the Summer '07 term at Ohio State.

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101pex1sol - Chemistry 101 - Su08 Solutions for Practice...

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