Chapter 5 (Gases) semester 1/ Substances that Exist as Gases 5.3 The Gas Laws 5.4 The Ideal Gas Equation 5.5 Gas Stoichiometry 5.6 Dalton’s Law of Partial Pressures 1

5.1 Substances that Exist as Gases Gases (Normal atmospheric condition = 25 °C & 1 atm) (i) Take the volume and shape of their containers (ii) Most compressible (iii) Mix evenly and completely when confined to the same container (iv) Low Densities Atmospheric Pressure -Pressure exerted by Earth’s atmosphere (measured by “Barometer”) 1 atm = 760 torr =7 60 mmHg = 76 cm Hg 2

5.3 The Gas Laws Boyle’s LawCharle’s &Gay-Lussac Law (i)Mathematical Expression (T, n constant) V  T ( P, n constant) (or) P  T (V,n const.) (ii) Problem Solving (iii) Graphical Presentation V (L) P(atm ) T(k) 3

Avogadro’s Law 5.4 The Ideal Gas Equation B. Law ….. C.Law ….. A.Law …. Combining… n=no. of moles m=mass in (g) M=molar mass d=density R=ideal gas constant for 1 mole of any gas 4

5.5 GAS STOICHIOMETRY STOICHEIONMETRON i.e ELEMENTMEASURE Two Greek Words i.e – CALCULATION ABOUT MASSES (SOMETIMES VOLUMES) OF REACTANTS & PRODUCTS. - VERY MATHEMATICAL PART OF CHEMISTRY Mole of reactantMass Mole of product Mass of Product 5

5.6 DALTON’S LAW OF PARTIAL PRESSURE P T = P A +P B +P C +…….. P A = X A P T X A = P B = X B P T ………etc. X B = X = MOLE FRACTION NOTE : FOR COLLECTION OF GAS OVER WATER ALWAYS DEDUCT WATER VAPOR PRESSURE FROM TOTAL PRESSURE i.e THE TOTAL PRESSURE OF A MIXTURE OF GASES IS JUST THE SUM OF THE PRESSURES THAT EACH GAS WOULD EXERT IF IT WERE PRESENT ALONE. 6