Chemical Foundations Goals: 1)Number of significant figures 2)Perform calculations involving sig figs 3)Dimensional Analysis Review 4)Determine density of solids and liquids and calculate volumes or masses using the given density 5)Review rules of nomenclature

Significant figures  Measurement of all of the certain digits in a measurement and the first uncertain digit (estimated number).

Rules for counting Sig Figs  1)Nonzero integers always count as significant figures  Ex. 1-9

Rules for counting Sig Figs  2)Zeros: There are three classes of zeros  Leading zeros precede all the nonzero digits and do not count as sig figs. Ex has 2 sig figs.  Captive zeros are zeros between nonzero numbers. These always count as sig figs. Ex has 4 sig figs  Trailing zeros are zeros at the right end of the number.  Trailing zeros are only significant if the number contains a decimal. Ex 1.00 * 10 2 has three sig figs  Trailing zeros are not significant if the number does not contain a decimal point. Ex 100 has 1 sig fig

Rules for counting Sig Figs  3)Exact numbers, which can arise from counting or definitions such as 1 in = 2.54 cm, never limit the number of significant figures in a calculation

Rules for Sig Figs in Calculations  1)For multiplication and division, the number of sig figs in the same as the number with the least number of sig figs in the calculation 40 x 3501 = answer?

Rules for Sig Figs in Calculations  2)For addition and subtraction, the result has the same number of decimal places as the number with the least number of decimal places in the calculation

Rules for Sig Figs in Calculations  3)Rules for rounding:  In a series of calculations, carry the extra digits to the final result, then round.  If the digit to be removed  Is less than 5, the preceding digit stays the same. For example 2.44 rounds to 2.4  Is greater than or equal to 5, the preceding digit is increased by 1. For example, 2.45 rounds to 2.5

Final Sig Figs slide  Significant Figures will always be counted in a grade!! LEARN THEM NOW!!

Density  Is the mass of substance per unit of volume of substance.  Density=mass/volume  Make sure you can solve for any of the 3 variables

Sample Density Problem  Density of an object can be determined through the water displacement method which means mass an object and then placed in a graduated cylinder and the volume is the amount of water displaced.  A sample containing g of metal pellets is poured into a graduated cylinder containing 12.7 mL of water, causing the water level in the cylinder to rise to 21.6 mL. Calculate the densityof the metal.

Dimensional Analysis  Is used to convert from one unit to another. It is the single most valuable mathematical technique that you will use in general chemistry.  Example The density of mercury is 13.6 g/cm 3. How many pounds would 1.00 liter of mercury weigh?

Nomenclature  Ionic Compounds  Cation Ion first then Anion Second  If monatomic anion change ending to –ide  If polyatomic need to use appropriate ending  PO 4 = phosphate  Covalent Bonds  Use Full name of first element and only prefix if there are more then one present  Change ending of second element to –ide and use a prefix to tell the number of elements involved in molecule

Nomenclature  Remember if you have transition metals you must include the charge on the metal by inserting roman numerals in parenthesis  EX MnO MnO 2

Naming Monatomic Acids  When you get an acid that is Hydro--ic acid and there is no oxygen in it you anion is monatomic. Then balance the charge of the anion with H +

Naming Polyatomic Acids Number of oxygen atoms Polyatomic ion name One more oxygen Perchlorate = ClO 4 - Home Base Chlorate = ClO 3 - One less oxygen Chlorite = ClO 2 - Two less oxygen Hypochlorite = ClO -

Naming Polyatomic Acids  When an acid contains a polyatomic anion, then the ending corresponds to the amount of oxygen in the anion. Acid prefixes and endings Prefixes and endings of anions Per –ic Per –ate -ic-ate -ous-ite Hypo -ous Hypo -ite

Naming Polyatomic Acids  Examples  H 3 PO 3 = ??  HNO = ??

Temperature Conversations  o C to o F  o C x (9/5) + 32= o F  o F to o C  o C to o K  o K = o C  9/5( o F – 32)= o C