Chapter 5 Chemical Reactions

The Mole

1 dozen eggs = 12 eggs 1 Gross pencils = 144 pencils 1 Ream of paper = 500 sheets of paper

The Mole 1 mole = 6.022 x 1023 things Avogadro’s number The number of carbon atoms in 12g of C-12 Abbreviation: “mol” How much does this weigh?

1 mole C atoms = 6.022 x 1023 Carbon atoms 6.022 x 1023 Carbon atoms = 1 mole of carbon atoms 1 mole bicycles = 6.022 x 1023 bicycles 6.022 x 1023 bicycles = 1 mole of bicycles 1 mole of anything = 6.022 x 1023 items of anything 6.022 x 1023 items of anything = 1 mole of anything

Cu, Al, Pb, S, Mg, Cr

Mole and Mass Relationships carbon 12.01 g 1 mole sulfur 32.06 g

Molar Mass The mass, in grams, of one mole of any element or compound Abbreviated with capital, italicized M Unit = grams/mole = g/mol Also called Formula Mass and Formula Weight

Problems You need 0.250 mol Cu for an experiment, how many grams should you use? How many atoms of Cu is this? You have 145.9 g Hg. How many moles are present?

Write the molecular formula or formula unit for the compounds above. Cl- Na+ Cl- Na+ Cl- Na+ Cl- Na+ Write the molecular formula or formula unit for the compounds above. What are the molecular and formula weights for the compounds above?

What is the mass of 1. 34 mole of the first compound What is the mass of 1.34 mole of the first compound? What is the mass of carbon in this sample? How many moles of Sodium Chloride are present in 9.29 g? How many moles of sodium are present in the sample?

How many oxygen atoms are there in 5.62g of Carbon Dioxide?

Your nurse gives you 10. 0g morphine, C17H19NO3 , for pain Your nurse gives you 10.0g morphine, C17H19NO3 , for pain. How many moles is this? How many grams of oxygen are present in this dose of analgesic?

Chemical Equations H2 (g) + Cl2(g)  2 HCl (g) Reactants Product(s) Coefficient Physical State Subscript H2 (g) + Cl2(g)  2 HCl (g) Reactants Product(s)

Law of Conservation of Matter/Mass Matter is neither created, nor destroyed, but is merely rearranged The mass of the reactants must equal the mass of the products H2 (g) + Cl2(g)  2 HCl (g)

Balancing Chemical Equations Zn(s) + HCl(aq)  H2(g) + ZnCl2(aq) Write the unbalanced equation Balance the atoms of one element Choose another element and balance it Continue until all elements have the same number of atoms on both sides of the equation Check yourself

5.2 Balancing Chemical Equations HOW TO Balance a Chemical Equation Write a balanced chemical equation for the reaction of propane (C3H8) with oxygen (O2) to form carbon dioxide (CO2) and water (H2O). Example Step [1] Write the equation with the correct formulas. C3H8 + O2 CO2 + H2O The subscripts in a formula can never be changed to balance an equation, because changing a subscript changes the identity of a compound.

5.2 Balancing Chemical Equations HOW TO Balance a Chemical Equation Balance the equation with coefficients one element at a time. Step [2] Balance the C’s first: Balance the H’s next:

5.2 Balancing Chemical Equations HOW TO Balance a Chemical Equation Balance the equation with coefficients one element at a time. Step [2] Finally, balance the O’s:

5.2 Balancing Chemical Equations HOW TO Balance a Chemical Equation Balance the equation with coefficients one element at a time. Step [2] Finally, balance the O’s:

5.2 Balancing Chemical Equations HOW TO Balance a Chemical Equation Check to make sure that the smallest set of whole numbers is used. Step [3]

Problems __ N2(g) + __ H2(g)  __ NH3(g) __ Fe(s) + __ Cl2(g)  __ FeCl3(s) __NH3(g) + __O2(g)  __NO(g) + __H2O(g) __C5H12(l) + __O2(g)  __CO2(g) + __H2O(g)

5.3 Types of Reactions The majority of chemical reactions fall into 6 categories: combination decomposition single replacement double replacement oxidation and reduction (Section 5.4) acid-base (Chapter 9)