Chemical Equations C5.6b Predict single replacement reactions.

Transcription

1 Chemistry 2SEM Chemical Equations C5.6b Predict single replacement reactions. Common Assessment Review Predict the following single replacement reactions: a. Zn + Pb(C2H3O2)2 ----> Pb + Zn(C2H3O2)2_ b. Fe + Al2O > NR c. 2AgNO3 + Ni > NR d. NaBr + I > NR Stoichiometry & Solutions C5.2d Calculate the mass of a particular compound formed from the masses of starting materials. How many grams of sulfuric acid (H 2 SO 4 ) are required to react completely with 15.0 grams of zinc in this single displacement reaction? Zn (s) + H 2 SO 4(aq) ----> ZnSO 4(aq) + H 2(g) Given Molar Mass Mole Ratio Molar Mass Answer 15.0g Zn 1 mol Zn 1 mol H 2 SO g H 2 SO g g Zn 1 mol Zn 1 mol H 2 SO 4 C5.2e Identify the limiting reagent when given the masses of more than one reactant. A 2.00 g sample of ammonia is mixed with 4.00 g of oxygen. What is the limiting reactant? 4 NH 3(g) + 5 O 2(g) 4 NO (g) + 6 H 2 O (g)

2 Given Molar Mass Mole Ratio Molar Mass Answer 2.00 g NH 3 1 mol NH 3 5 mol O g O g g NH 3 4 mol NH 3 1 mol O g Actual amount Answer 4.00g O g_O 2 Is there enough in your actual to take this amount out??? Limiting Reactant = O 2 What are the relationships between? a. volume and temperature volume increases, temp. increases (direct) b. pressure and temperature pressure increases, temp. increases (direct) c. pressure and volume pressure increases, volume decreases (indirect) What tool or device can you use to determine the above information? Explain how to use it. PTV 1. Write it on your paper 2. Place finger on the variable that is held constant 3. Move the one variable that increases or decreases and then see what happens to the other variable.

3 When a solid, liquid, and gas are all at the same temperature, what is the average kinetic energy? the same average kinetic energy (just different intermolecular forces) What is the relationship between melting points or boiling points, intermolecular forces, and strengths? -The stronger the intermolecular force, the higher the melting and boiling points -If you are comparing substances that have the same type of intermolecular force, then look at mass of the substances. The heavier the substance, the higher the melting and boiling points.! " " # " $ " %&$!"!"!#!$!%! "&'!"""! "!"#!!'! "!"!"!"! ($!&"&#!!"! ($!&"&

4 $'(! What elements are involved with hydrogen bonding? hydrogen attached to N, O, F )!"&*%+"+,"-$ )! +! ' **+,! + $-!./ 1. Draw the Lewis structure for H 2 O, CO 2, CH 4, PH 3, and SiH 4. H O H O = C = C H H P H H I I I polar nonpolar H C H H H Si H I I H H 2. Identify the type of polarity for the above structures in #1. Given above nonpolar polar nonpolar 3. Identify what type of intermolecular force each of the following structures would have. H 2 O - Hydrogen bonding (hydrogen is attached to O) N,O, F CO 2 - London Dispersion (between nonpolar molecules) CH 4 - London Dispersion (between nonpolar molecules) PH 3 - Dipole-dipole (between dipole molecules other than hydrogen w/ N, O, F) SiH 4 London Dispersion (between nonpolar molecules)

5 4. Which of the following would have the lowest melting point? Highest melting point? Using the above information about intermolecular forces for these compounds: a. Why? H 2 O - CO 2 - (44.0g) CH 4 - (16.0g) PH 3 - SiH 4 (32.0g) Answers above Lowest MP Highest MP X (Dispersion forces weakest and X (hydrogen bonding) (strongest IMF) this is lightest of all the dispersion) b. What are the steps you use to determine high or low melting points?. Draw Lewis structures for all compounds 2. Determine type of intermolecular force 3. Apply strengths of IMF Identify the states of matter. What is the relationship between states of matter and kinetic energy at the same temperature? What type of intermolecular forces do they each have? Why then, 5. K.E. (a) IMF (b) solids lowest amt. strongest liquids gases highest amt. weakest

6 +0!1 If I have 5.6 liters of gas in a piston at a pressure of 1.5 atm and compress the gas until its volume is 4.8 L, what will the new pressure inside the piston be? V 1 P 1 = V 2 P 2 P 2 = V 1 P 1 = (5.6L)(1.5atm) = 1.8 atm V 2 4.8L +&0!1 If the pressure of carbon dioxide is 920 mmhg and this gas is collected at 1200 o C, what will the what will the pressure of this gas be after it cools to 25 0 C, with volume constant? P 1 = P 2 T 1 T 2 T1 = 1200oC = 1473 K T2 = 25oC = 298 K P 2 = P 1 T 2 = (920 mmhg)(298k) = 186 mmhg T 1 (1473K) +0! 1 If I have 45 liters of helium in a balloon at 25 0 C and increase the temperature of the balloon to 55 0 C, what will the new volume of the balloon be? V 1 = V 2 T 1 T 2 T 1 = 25oC = 298 K T 2 = 55oC = 328 K

7 V 2 = V 1 T 2 = (45L)(328K) T 1 (298K) +2 2 a. freezing -exothermic (energy is being released, lowering KE, increasing PE) b. melting -endothermic c. vaporization -endothermic d. condensation -exothermic e. sublimation -endothermic f. deposition -exothermic exothermic- energy is being released from the system endothermic- energy is absorbed into the system +0 Ethylene (C 2 H 4 ) burns in oxygen to form carbon dioxide and water vapor: C 2 H 4(g) + 3 O 2(g) 2 CO 2(g) + 2 H 2 O (g) How many liters of water can be formed if 1.25 liters of ethylene are consumed in this reaction? 1.25L C 2 H 4 2L H 2 O = 2.50 L H 2 O 1L C 2 H 4 Solutions C3.4g Explain why gases are less soluble in warm water than cold water. gas solubility decreases when temperature increases Explain and sketch what this relationship would look like on a graph? An inverse relationship

8 Compare and contrast cold pop and warm pop. Cold pop- lower temp. so will have higher gas solubility Warm pop- higher temp. so will have less gas solubility C4.7a Investigate the difference in the boiling point or freezing point of pure water and a salt solution. salt will raise the boiling point and lower the freezing point salt interrupts the production of the ice crystal when freezing water salt interrupts the evaporation of liquid water, lowering vapor pressure, so much increase temperature to get vapor pressure = atmospheric pressure Describe an example for Freezing Point Depression: Salt being thrown on icy roads in the winter Anti-freeze being put in engine so liquid won t freeze in engine Boiling Point Elevation: Making spaghetti- boiling the water and adding salt to increase the boiling point. Chemical Reactions and Energy C2.3a Explain how the rate of a given chemical reaction is dependent on the temperature and the activation energy. Temperature increases KE, which will increase # of collisions, which increase the rate of reaction The more activation energy needed to start the reaction, the slower the reaction rate. C2.3b Draw and analyze a diagram to show the activation energy for an exothermic reaction that is very slow at room temperature. In diagrams showing an exothermic reaction, the reactants will have more energy(be higher) than the product energy (lower)

9 The higher the activation energy hill, the slower the rate of reaction. slower reaction faster reaction Catalysts can lower the activation energy for the reaction to occur faster

10 C3.1b Draw enthalpy diagrams for exothermic and endothermic reactions. exothermic reaction endothermic reaction

11 C3.1c Calculate the H for a chemical reaction using simple coffee cup calorimetry. q = m x t x c (H) Remember the math in the Snack Lab Sample problem: How much heat is required to raise 15.0 g of water from 20.0 C to 50.0 C? (water s specific heat = 4.18J/goC) q or H = mass x specific heat x t = 15.0g x 4.18 J/g oc x (50.0oC oc) = 1881 J C3.1d Calculate the amount of heat produced for a given mass of reactant from a balanced chemical equation. Stoichiometry with a heat reaction Sample problem: How much heat must be absorbed to decompose 5.00 grams of ammonia? 92 kj + 2 NH3 N2 + 3 H2 mass x 1 mole x heat = molar mass mole ratio 5.00g x 1 mole x 92 kj = 27.0 kj g 2 mol C3.4d Draw enthalpy diagrams for reactions and products in endothermic and exothermic reactions. See C3.1b above Equilibrium C5.3a Describe equilibrium shifts in a chemical system caused by changing conditions (Le Chatelier s Principle).

12 What would happen to the position of the equilibrium when the following changes are made to the equilibrium system below? (a) SO 2 is added to the system. 2SO 3 (g) 2SO 2 (g) + O 2 (g) Reverse reaction favored. Increase [SO3], Decrease [O2] (b) SO 3 is removed from the system. Reverse reaction favored. Decrease [SO2] and Decrease [O2] (c) O 2 is added to the system. Reverse reaction favored. Increase [SO3], Decrease [SO2] C5.3b Predict shifts in a chemical system caused by changing conditions (Le Chatelier s Principle). Predict the effect of decreasing the temperature on the direction of the following equilibrium. (a) H2(g) + Cl2(g) 2HCl(g) kj shifts forward or reverse (b) 37.2 kj + 2NH3(g) N2(g) + 3H2(g) shifts forward or reverse (c) CO(g) + H2O(g) CO2(g) + H2(g) kj shifts forward or reverse C5.3c Predict the extent reactants are converted to products using the value of the equilibrium constant. If K > 1, products are favored (forward reaction is favored at equilibrium) for example: K= 3.4

13 Acids and Bases If K < 1, reactants are favored (reverse reaction is favored at equilibrium) for example: K=0.025 If K = 1, neither reactants nor products are favored (no reactions is favored at equilibrium) for example: K= 1 C5.7f Write balanced chemical equations for reactions between acids and bases and perform calculations with balanced equations. When an acid reacts with a base they always produce two products. What are they? H2O and salt Titrations Sample Problem: If it takes 54 ml of 0.1M NaOH solution to neutralize 125 ml of an HCl solution, what is the concentration of HCl? HCl + NaOH -----> H 2 O + NaCl (0.1M)(.054L) = moles NaOH moles NaOH x 1 mole HCl = moles HCl 1 mole NaOH moles HCl = HCl L C5.7g Calculate the ph from the hydronium ion or hydroxide ion concentration. 1. Determine the ph of a 4.5 x 10-3 M HBr solution. ph = If a solution has a [H + ] concentration of 4.5 x 10-7 M, what is the ph of the solution? Is this an acidic or basic solution? ph = 6.3