Chemistry

Gas Laws Standard Temperature and Pressure (STP) Standard temperature: 0?C or 273 K Standard pressure:1 atm, 760 mm Hg, or 101.3 kPa Boyle?s Law The pressure of a dry gas is inversely proportional to its volume if the temperature is held constant. Inverse Proportion two terms related so that, if one term increases, the other term decreases Boyle?s Law P V , PV = k P1V1 = P2V2 As pressure increases, volume decreases. 6 Chemistry textbook, p. 250 7 Chemistry textbook, p. 250 P1V1 = P2V2 Sample Problem 1 A sample of gas occupies 352 mL at a pressure of 3.17 atm. If the P is reduced to 1.24 atm, what volume will result? (3.17 atm)(352 mL) = (1.24 atm)V2 900 mL = V2 A sample of gas occupies 200 mL at a P of 2.15 atm. If the P is reduced to 1.25 atm, what is V2? 344 mL 537 mL 98 mL 89 mL

Stoichiometry 1 Literally means ?to measure the elements? Answers questions like?How much is needed?? and ?How much is produced?? Stoichiometry Unit analysis 365 days 1 year 24 hrs 1 day 3600 sec. 1 hr 1 year How many seconds are in a year? = 31,536,000 sec. Unit analysis We use unit analysis in stoichiometric problems also. Grams-to-moles conversion factors are found in the periodic table. Unit analysis Mole-to-mole conversion factors are found in the coefficients of the equation. A mole-to-mole conversion changes moles of one substance to moles of another substance. ?Skeleton Equation?

Writing Equations Chemical Equations Math equations show equalities. Chemical equations show processes (one chemical changes to another chemical). A Chemical Equation Must: Identify all the substances involved. Show the composition of the substances (use formulas). A Chemical Equation Must: Account for all the atoms. (There must be the same number of atoms of every element on both sides of the equation.) Parts of an Equation Reactants Products Coefficients Arrow Example reactants Ca(HCO3)2 + Ca(OH)2 2 H2O + 2 CaCO3 products The ?2? is a coefficient to tell how many molecules of each compound are present. What tells you how many atoms of an element are in a molecule? Symbol Subscript Coefficient Catalyst Question 7 Special Symbols in Equations g?: A gas was produced.