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CHMA10H3 Lecture Notes - Lecture 1: Covalent Bond, Sulfuric Acid, Hydronium

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24 Sep 2016

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CHMA10H3 Full Course Notes

CHMA10H3 Full Course Notes

Document Summary

Chemical reaction: substances converted into different ones. Combustion reaction: substance combines with oxygen to more one or more oxygen containing compounds; produces heat. Heat produced by combustion reaction supplies society"s energy needs > e. x. com- bustion of natural gas to cook food, heat homes and burning fossil fuels (coal, oil) for electricity. Chemical equation > reactants on left side of equation and products on right side. (g) gas, (l) liquid, (s) solid, (aq) aqueous. Chemical reactions must be balanced to not violate the law of conservation of mass (mass is neither created nor destroyed; mass of products=mass of reactants) Adding coefficients changes the number of molecules of a substance. Rule for balancing: always balance atoms in compounds before atoms in pure ele- ments. Chemical reactions that involved reactants dissolved in water are the most common and important. A homogenous mixture of two substances is a solution (major component is solvent and minor is solute)

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Chemical Reactions and Equations Learning objectives To observe physical and chemical properties associated with chemical changes To be able to give evidence for the occurrence of a chemical reaction To write a balanced chemical equation To identify areaction as a combination, decomposition, precipitation, single or double replacement, or combustion reaction ntroduction When a substance undergoes a physical change, it changes its appearance but not its composition. For example, when ice melts to form water, it undergoes a physical change from solid to liquid. In a chemical change, the composition of a substance is changed to give a new substance with different physical and chemical properties. For example, when silver tarnishes, the shiny silver (Ag) changes to a dull gray silver sulfide (AgaS). Not only has the chemical formula changed from Ag to Agus, but also the physical properties (shininess) of the substance have changed. Some examples of physical and chemical changes are listed in Table 1 below. Table 1. Comparison of Physical and Chemical Changes Examples of Physical changes Examples and Evidence of Chemical Changes Change in state (melting, freezing, evaporating Formation of a gas (bubbles) subliming) Formation of a solid (precipitate) Change in size Tearing Change in Color Heat is given off or absorbed A solid dissolving in a solvent In a chemical reaction, atoms in the reactants are rearranged to produce new combinations of atoms in the products. However, the total number of atoms of each element in the reactants is equal to the total number of atoms in the products. This is true according to the Law of Conservation of Mass, which states that the total mass remains constant during a chemical reaction. In other words, matter cannot be created or destroyed in a chemical reaction. In a chemical equation, the reactants are shown on the left and the products are on the right. An arrow in between indicates that a chemical reaction occurs. Finally, the physical state of each compound is designated in parentheses after the chemical formula. Solid, liquid, gas, and aqueous (dissolved in water) are shown as(s,(n,(g), and (aq), respectively.

Science Tutor: Chemistry Name: Mixtures, Solutions, &Compounds: Chemical Equations Date Chemical Equations If a chemical symbol can be thought of as a letter and a chemical formula as a word in the language of chemistry, then a chemical equation is a statement or sentence. A chemical equation is a shorthand way of describing a chemical reaction between two or more substances. A "+ sign means "combines with." An arrow points away from the reactants and toward the products (See page 10), and an arrow means "yields." 2Na + Cl2 â 2NaCl means sodium combines with chlorine to yield sodiumn chloride (salt) Look closely at the equation above. Notice the "2" in front of NaCI on the right and Na on the left. That 2, called a coefficient, is necessary to make this equation balance. Remember Antoine Lavoisier? (Page 15) Matter is neither created nor destroyed in a chemical reaction. The same number of each kind of atom must be on both sides of a chemical equation. Because chlorine only exists as a molecule consisting of two chlorine atoms, it requires two atoms of sodium to yield two molecules of salt (NaCI). This illustrates another important law stated clearly by the French chemist Joseph-Louis Proust in 1799. Chemical compounds always combine in certain specific fixed proportions. Wherever sodium and chlorine combine, two atoms of sodium will be necessary to react with one molecule of gaseous chlorine. 1 . For the equation 2Mg + O2â 2MgO + energy: A. List the reactant or reactants 2Hato B. List the product or products C. How many atoms of magnesium does it take to combine with one molecule of oxygen? D. How many molecules of magnesium oxide are produced in this reaction? 2. Hydrogen can combine with oxygen to produce water. We could write the equation like this: H2 + O2 â H2O. But this equation is unbalanced! Rewrite this equation with the correct coefficients so that an atom of oxygen doesn't disappear! (Be careful. If you add a coefficient to one side you may have to adjust the other. Count all the atoms.) 3. Now that you have the idea, balance the following equations: A, Pho, â PbO + 02 C. Ca + H2O â Ca(OH)2 + H2 How is following a recipe to mix up a batch of biscuits (or any other food item) similar to Proust's law for chemical reactions? 4. OMark Twain Media, Inc., Publishers 17

7.
Calculate the percentage, by mass, of fluorine in sulfurhexafluoride (SF6), a potent greenhouse gas.
A) 78.0%
B) 59.2%
C) 22.0%
D) 82.1%
E) 85.7%

8.
Octane (C8H18) is one of the principal components of gasoline. Howmany moles of CO2 are produced during the combustion of 3.0 mol ofoctane?
Unbalanced equation: C8H18 + O2 --> CO2 + H2O
A) 3.0
B) 26
C) 24
D) 8.0
E) 4

9.
How many atoms are present in 0.375 mol of palladium (Pd)atoms?
A) 6.23 x 1021
B) 2.26 x 1023
C) 6.02 x 1023
D) 1.61 x 1024
E) 2.12 x 1021

10.
How many molecules are present in 1.0 kg of hydrogen (H2)gas?
A) 6.0 x 1023
B) 3.0 x 1026
C) 6.0 x 1026
D) 3.0 x 1023
E) 1.7 x 1025

11.
What evidence indicates that the rising atmospheric CO2 levels arecaused by the combustion of fossil fuels?
A) Both the average global temperature and the atmospheric CO2level have risen.
B) The 14C/12C ratio in atmospheric CO2 is unusually low.
C) Increased precipitation in most of the NorthernHemisphere.
D) The 18O/16O ratio in atmospheric CO2 is the same as inatmospheric oxygen.
E) The level of atmospheric moisture has increased.

12.
Heat is a form of
A) Energy
B) Pressure
C) Work
D) Volume
E) Temperature

13.
Oxygenated gasolines
A) Are gasolines that have oxygen gas bubbled through them
B) Contain nitrogen containing compounds
C) Are formulated to contain water
D) Have higher activation energies for combustion than regulargasolines.
E) May contain MTBE or ethanol

14.
A chemical reaction accompanied by a release of energy is calleda/an ______ reaction.
A) exothermic
B) fast
C) activated
D) catalyzed
E) endothermic

15.
The diagram below shows a simplified version of a fractionatingcolumn used in the petroleum industry.

The compounds with the lowest boiling points are condensed atposition

A) C.
B) D.
C) B.
D) A.

16.
Where is most of the carbon on earth stored?
A) in the form of fossil fuels
B) in the deep ocean
C) in the atmosphere
D) in surface water
E) in the forests and soil

17.
Find the molar mass of ethanol, C2H6O.
A) 22.1 g/mol
B) 26.0 g/mol
C) 46.07 g/mol
D) 45.06 g/mol
E) 29.02 g/mol

18.
Determine the shape or geometry of PH3. (Hint: Use the PeriodicTable to arrive at the electron configuration forphosphorous.)
A) trigonal planar
B) linear
C) trigonal pyramidal
D) bent
E) tetrahedral

19.
The energy stored in the chemical bonds of fossil fuels is a formof ______ energy.
A) nuclear
B) potential
C) mechanical
D) kinetic
E) electrical

20.
The heat of combustion of methane, CH4, is 50.1 kJ/g. How much heatwould be generated if 1.00 mol of methane undergoes completecombustion?
A) 50.1 kJ
B) 804 kJ
C) 601 kJ
D) 0.32 kJ
E) 3.12 kJ

21.
Methane is approximately 23 times more powerful than carbon dioxideas a greenhouse gas. Which are significant sources of methaneemissions?
I. The digestive systems of ruminants (cows, sheep, etc.)
II. Automobile exhaust
III. Rice cultivation
IV. Decaying wetland vegetation
A) I and II only
B) I only
C) All of these
D) II only
E) I, III, and IV only

22.
Which atmospheric component does not contribute to globalwarming?
A) CH4
B) CO2
C) CFC
D) N2
E) H2O

23.
What is the effect of infrared energy on matter?
A) It breaks chemical bonds.
B) It excites bonding electrons.
C) It increases molecular rotation.
D) It increases the vibration of chemical bonds.
E) It excites non-bonding electrons.

24.
According to current estimates, the fuel in greatest abundance onearth is
A) natural gas.
B) hydrogen
C) uranium.
D) coal.
E) petroleum.

25.
A gasoline's octane rating is a measure of the
A) purity of the gasoline.
B) energy content of the gasoline.
C) percent of gasoline that contains octane
D) pollutants produced by burning the gasoline in a vehicle'sengine.
E) gasoline's resistance to causing knocking in a vehicle'sengine.

26.
Advertising claims sometimes state that adding something mechanicalto a car's engine will allow it to recover 100% of the energy thatcomes from burning gasoline. You should be skeptical of such claimsbecause they are not consistent with the
A) first law of thermodynamics.
B) energy difference between reactants and products
C) second law of thermodynamics.
D) law of conservation of matter.
E) activation energy requirements of all chemical reactions.

27.
In order to make useful predictions, which factors must beaccounted for by climatic models?
I. Cooling effect of atmospheric aerosols
II. Smoke, haze, and cloud cover
III. Change in land use
IV. Combustion of fossil fuels
A) III and IV only
B) II, III, and IV
C) II and III only
D) I, II, III, and IV
E) IV only

28.
Use the equation to help you calculate the heat of combustion ofethylene, C2H4. The bond energies are: C H 416 kJ/mol; C C 598kJ/mol; O O 498 kJ/mol; C O 803 kJ/mol; H O 467 kJ/mol.

The heat of combustion of ethylene is

A) 1216 kJ/mol.
B) 220 kJ/mol.
C) 1324 kJ/mol.
D) 754 kJ/mol.
E) 242 kJ/mol.

29.
Scientists believe they know the average global temperature overthe last 160,000 years. Which property of the ice core samples fromAntarctica provides this information?
A) the 1H/2H ratio
B) the density of the ice
C) the thickness
D) the temperature
E) the carbon dioxide concentration

30.
(Both the Clinton) and the George W. Bush administrations have beenunwilling to sign the Kyoto Protocol. What has been a stated reasonfor their objection to the treaty?
A) Enforcement of the treaty will be impossible.
B) Lack of conclusive evidence that increased atmospheric CO2 leadsto global warming.
C) The target emission levels are not sufficiently low to affectthe greenhouse effect.
D) The treaty does not include a provision for trading emissionallowances.
E) Developing countries are not required to control greenhouse gasemissions.