Chemical Equations

Numbers and Formulas What’s the Difference? H2 2H See Diatomics 2H2 2H2O See Diatomics

Your Turn #1: Draw what each of the following look like: 3BH2Cl How many H’s How many B’s, H, Cl

Na + Cl2  NaCl “Reacts with” --or-- “and” “To yield” --or-- “produce” Reactants Product “Sodium reacts with chlorine to produce sodium chloride”

Including States in Equations (s), (l), (g), mean solid, liquid, and gas (aq) means aqueous _______________ () means precipitate or solid (↑) means gas is produced KCl(aq) + AgNO3(aq)  KNO3(aq) + AgCl(s) (dissolved in water)

Symbols Above the Arrow: Pt CO(g) + O2(g) CO2(g) Any other compound or element means a catalyst Catalyst - a substance that aids in the process of a chemical reaction without itself being used up or changed. Catalysts help to speed up reactions Enzymes are examples of catalysts within the body

Symbols Above the Arrow: HgO(s) 2Hg(l) + O2(g) Means that heat is added “ “ is Greek letter Delta, which is often used to represent “change in” Literally means “change in heat” Heat generally acts like a catalyst to help many reaction go faster (more collisions)

Other Ways to show Energy Change Endothermic: Energy Is Added/ Needed/ Required ΔH HgO(s) 2Hg(l) + O2(g) HgO(s) + energy 2Hg(l) + O2(g) HgO(s) + 45.7kJ 2Hg(l) + O2(g) C3H8(g) + 5O 2(g) 4H2O(g) + 3CO 2(g) + energy C3H8(g) + 5O 2(g) 4H2O(g) + 3CO 2(g) + 2,220kJ Exothermic: Energy is Produced / Given Off

When burning methane, is fire a Product or a Reactant Energy Change – FIRE ? CH4(g) + O 2(g) 2H2O(g) + CO 2(g) + energy In Exothermic reactions, the reaction gives off energy. The “fire” that you see is the heat and light energy that is given off Fire is a result of the reaction, not added to it.

Demo Barium hydroxide + ammonium thiocyanate Potassium permanganate + glycerin

Your Turn #2: Write a formula equation for the following Solid potassium nitrate is heated to produce gaseous oxygen and solid potassium nitrite Ammonia gas (NH3) is reacted with oxygen in the presence of a platinum-rhodium catalyst to produce nitric acid (all acids are aqueous)

Your Turn: Log in to computer and open HW: Packet Pages 9-11 Stu_Lab SH_Students ChemCD Balancing Equations Balancing.pps

Factors Affecting Rates of Chemical _ Reactions (Bottom of Packet Page P8) Catalysts Concentration The ________ the concentration, the _______ the rate of reaction Surface Area The _______ the exposed surface area, the ________ the rate of reaction Temperature The higher the temperature, the _______ the rate of the reaction because more _________ are occurring at a given time. Agitation

Balancing Equations Write the word equation for the reaction Write the formula for each substance Make sure all compounds add up to zero Watch out for diatomic elements Work one element at a time and adjust the coefficients to make the same on both sides Do NOT Touch the Subscripts!!! Save H & O for last Make sure cofficients are in lowest whole number ratio

Balancing Equations: Example #1 potassium chlorate  potassium chloride + oxygen

Balancing Equations: Example #2 Barium nitrate + Aluminum Aluminum nitrate + Barium

Balancing Equations: Your Turn Iron + oxygen  Iron(III) oxide

What does it mean if an element is Diatomic ? “Regular” Elements Diatomic Elements What does it mean if an element is Diatomic ?

Ar N2 C O2 Symbol “Regular” Elements Diatomic Elements Nitrogen Argon Carbon Oxygen C O2

What Elements are Diatomic? Hydrogen (H2) The -gens and the -ines are diatomic Nitrogen (N2) Oxygen (O2) Fluorine (F2) Chlorine (H2) Bromine (Br2) Iodine (I2)

Halogens Back