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?

Types of Reactions Types of Reactions There are four types of reactions. Synthesis Decomposition Single replacement Double replacement Occurs when two substances unite Synthesis A + B AB Synthesis 2 Mg + O2 2 MgO magnesium(element) oxygen(element) magnesium oxide(compound) 4 Occurs when a substance splits into parts Decomposition AB A + B Decomposition hydrogen(element) oxygen(element) water(compound) 2 H2O 2 H2 + O2 6 Occurs when a more active substance replaces one part of a compound that is less active Single Replacement Y X + X Y Z Z + Single Replacement hydrogen(element) potassiumhydroxide(compound) water(compound) potassium(element) 2 K + 2 H2O H2 + 2 KOH 8 These reactions are also called displacement or substitution reactions. Single Replacement