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# Chemistry SCH4U

This course enables students to deepen their understanding of chemistry through the study of organic chemistry, energy changes and rates of reaction, chemical equilibrium, atomic and molecular structure, and electrochemistry. Students will further develop problem-solving and laboratory skills as they investigate chemical processes, at the same time refining their ability to communicate scientific information. Emphasis will be placed on the importance of chemistry in daily life, and on evaluating the impact of chemical technology on the environment. Prerequisite: Grade 11 Chemistry SCH3U

CXHYOH

# Structure and Properties of Matter

## Draw lewis diagrams for the following molecules using the rules below:

 Step What to Do 1 Arrange the atoms with the element that forms most bonds in the central position. 2 Add the total number of valence electrons. 3 Start by placing one bonding pair of electrons between each atom. 4 Put remaining electrons as lone pairs on all atoms except central atom, to a maximum octet of 8 electrons per atom. 5 If octet on central atom is incomplete, move peripheral lone pairs into bonding electrons that are shared with the central atom. 6 Make sure central and peripheral atoms have complete octets. Now if there are extra electrons, place these as lone pairs on the central atom (*exception to octet rule).

# Thermochemistry - Energy Changes

Specific Topic General Topic School Date
Enthalpy of Reaction ∆Hrxn Equation North Toronto Nov 2013
Enthalpy of Reaction ∆Hrxn Hess's Law North Toronto Nov 2013

## The following values are all used in the questions below.

 boiling point N2 (l) = -196˚C melting point N2 (s) = -210˚C enthalpy of vaporization N2 (l), Hvap = 199 J/g enthalpy of fusion N2 (l), Hfus = 25.7 J/g specific heat N2 (g), c = 1.34 J/gK specific heat N2 (l), c = 2.042 J/gK specific heat N2 (s), c = 2 J/gK boiling point NH3 (l) = -33˚C enthalpy of vaporization NH3 (l), Hvap = 1,370 J/g specific heat NH3 (l), c = 4.7 J/gK specific heat NH3 (g), c = 1.64 J/gK

# ENTROPY

## Ethanol reacts with excess oxygen in a combustion reaction to produce carbon dioxide and water, both in gaseous states. Use the standard state (298 K) enthalpy of formation (Hf˚) and entropy (S˚) in the table to answer the questions.

 ∆Hf˚ (kJ/mol) ∆S˚ (J/mol·K) C2H6O (l) -278 160 O2 (g) 0 205 CO2 (g) -394 214 H2O (l) -286 70

## Given the molar enthalpy of fusion and vaporization of ice and water below...

 ∆ Hfusion ice 6 kJ/mol = 6,000 J/mol ∆ Hvaporization water 40.7 kJ/mol = 40,700 J/mol

# Kinetics - Rates of Reactions

A + 2B → 3C + D

## The table contains the experimental information for the reaction given below, at a certain temperature.

3A + B + C → 2D + E
 Test Initial [A] (mol/L) Initial [B] (mol/L) Initial [C] (mol/L) Rate of Production of E (mol/(L·s)) 1 0.4 0.2 0.3 0.75 × 10-2 2 0.8 0.2 0.3 3.0 × 10-2 3 0.4 0.4 0.3 1.5 × 10-2 4 0.4 0.2 0.6 3.0 × 10-2

## Given the overall reaction and the mechanism steps...

$A + 3B + C \xrightarrow{} AB + E$ $\begin{array}{lcl} \text{Step 1:} \quad A + 2B & \xrightarrow{} & AB + B \quad (fast) \\ \text{Step 2:} \quad B + C & \xrightarrow{} & D \quad (fast) \\ \text{Step 3:} \quad B + D & \xrightarrow{} & E \quad (slow) \\ \end{array}$

## Given the integrated rate law for first order reactions, where [A]t is the concentration at time 't', k is the rate constant, and ln[A]0 is the initial concentration of the reactant.

ln[A]t = -kt + ln[A]0

## Half-life equations mostly follow first order kinetics. Given:

ln[A]t = -kt + ln[A]0

## Given the integrated rate law for second order reactions, where [A]t is the concentration at time 't', k is the rate constant, and ln[A]0 is the initial concentration of the reactant.

$\dfrac{1}{[A]_t} = kt + \dfrac{1}{[A]_0}$

# Chemical Systems and Equilibrium

## Given the following reaction...

$Ca_3(PO_4)_{2(s)} \longleftrightarrow 3Ca^{2+}_{(aq)} + 2PO^{3-}_{4(aq)}$

## Given the general equation below...

$X_aY_{b (s)} \longleftrightarrow aX_{(aq)} + bY_{(aq)}$

## Nitrate salts are typically highly soluble and can be assumed to dissociate completely. Solid silver nitrate, AgNO3 is dissolved until saturation in water at 1 atm at the three different temperatures in the test tubes below.

 Tube A, 20˚C Tube B, 60˚C Tube C, 100˚C 12.7 M 25.9 M 43.1 M

## The breakdown of ammonia is the reverse of the Haber process. Calculate the reaction quotient, q for the breakdown of ammonia under certain conditions...

$2NH_{3 (g)} \longleftrightarrow N_{2 (g)} + 3H_{2 (g)}$

## Mixing 0.15 L of a 0.02 M solution of lithium carbonate with 0.02L of 0.1 M solution of zinc fluoride...

\begin{align} Li_2CO_{3 (s)} \longleftrightarrow 2Li^{+}_{(aq)} + CO_{3 (aq)}^{2-} \\ \\ ZnF_{2 (s)} \longleftrightarrow Zn^{+}_{(aq)} + 2F^{-}_{(aq)} \\ \\ \end{align}

## A solution contains an initial 0.001 M concentration of fluoride and sulfate ions. Good luck!

\begin{align} SrF_{2 (s)} \longleftrightarrow Sr^{2+}_{(aq)} + 2F^{1-}_{(aq)} \quad\quad k_{sp} = 4.3 × 10^{-9} \\ \\ SrSO_{4 (s)} \longleftrightarrow Sr^{2+}_{(aq)} + SO^{2-}_{4 (aq)} \quad\quad k_{sp} = 3.4 × 10^{-7} \\ \\ Sr(ClO_3)_{2 (s)} \longleftrightarrow Sr^{2+}_{(aq)} + 2ClO^{1-}_{3 (aq)} \quad \text{very soluble} \\ \\ \end{align}

## The solubility product constant (Ksp) of calcium sulfate and silver sulfate are given at 25˚C.

\begin{align} K_{sp} \ CaSO_4 = 4.9 × 10^{-5} \\ \\ K_{sp} \ Ag_2SO_4 = 1.2 × 10^{-5} \\ \\ \end{align}

## The solubility product constant of barium nitrate Ba(NO3)2 at 25˚C is,

\begin{align} K_{sp} = 4.6 × 10^{-3} \\ \\ \end{align}

# Acid-Base Equilibrium

## Ammonia is a common household cleaner that is highly soluble in water. A solution of ammonia forms ammonium and hydroxide in solution according to the following equation.

$NH_{3(aq)} + H_2O_{(l)} \longleftrightarrow NH^+_{4(aq)} + OH^-_{(aq)}$

## Phosphoric acid, H3PO4 is a triprotic acid that dissociates fully into phosphate ions. The acid solubility constants are given below.

Ka 1 = 7.5 × 10-3
Ka 2 = 6.2 × 10-8
Ka 3 = 2.2 × 10-13