* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download one
Gas chromatography–mass spectrometry wikipedia , lookup
California Green Chemistry Initiative wikipedia , lookup
Nuclear transmutation wikipedia , lookup
Organic chemistry wikipedia , lookup
Electrolysis of water wikipedia , lookup
Nuclear fusion wikipedia , lookup
Chemistry: A Volatile History wikipedia , lookup
Chemical plant wikipedia , lookup
Drug discovery wikipedia , lookup
Registration, Evaluation, Authorisation and Restriction of Chemicals wikipedia , lookup
Chemical potential wikipedia , lookup
Enantioselective synthesis wikipedia , lookup
Chemical industry wikipedia , lookup
Safety data sheet wikipedia , lookup
History of chemistry wikipedia , lookup
Supramolecular catalysis wikipedia , lookup
Isotopic labeling wikipedia , lookup
Multi-state modeling of biomolecules wikipedia , lookup
Asymmetric induction wikipedia , lookup
Photoredox catalysis wikipedia , lookup
Atomic theory wikipedia , lookup
Ring-closing metathesis wikipedia , lookup
Electrochemistry wikipedia , lookup
Determination of equilibrium constants wikipedia , lookup
Equilibrium chemistry wikipedia , lookup
Marcus theory wikipedia , lookup
Hydrogen-bond catalysis wikipedia , lookup
Process chemistry wikipedia , lookup
Photosynthetic reaction centre wikipedia , lookup
Rate equation wikipedia , lookup
Physical organic chemistry wikipedia , lookup
Strychnine total synthesis wikipedia , lookup
Chemical equilibrium wikipedia , lookup
Lewis acid catalysis wikipedia , lookup
Bioorthogonal chemistry wikipedia , lookup
George S. Hammond wikipedia , lookup
Click chemistry wikipedia , lookup
Chemical reaction wikipedia , lookup
Chemical thermodynamics wikipedia , lookup
Chemical Reactions Chapter 7 Chap 7 Pretest • Which of the following is an example of a physical change? • • • • A. B. C. D. Wood burns and becomes ash. A steel nail rusts over time. Ice melts and becomes water. Milk curdles when acid is added to it. Chap 7 Pretest • Which of the following characteristics can you determine about a substance based on its chemical formula? • A. The number and types of atoms that make up a substance. • B. The mass of an unknown sample of the substance. • C. The melting point of the substance. • D. The density and state of the substance at room temperature. Chap 7 Pretest • How do you find the atomic mass of an element? • The atomic mass of each element is listed on the periodic table. Chap 7 Pretest • Which conversion factor would you multiply 0.020 m by in order to express the quantity in centimeters? • • • • A. B. C. D. 1000 m/1 km 1 km/1000 m 1 m/ 100 cm 100 cm/1 m Equation Analogy • Imagine that you work at a skateboard shop and you are in charge of assembling the skateboards. Every skateboard requires one deck (the board), two trucks (the mounted axels), and four wheels. • Your boss asks you to make five skateboards. How many trucks do you need? • The following diagram shows the “recipe” for one skateboard. What do you notice about the relative amounts of each part on either side of the arrow? + + 1D + 2T + 4W D 1T 2W 4 One deck plus two trucks plus four wheels makes one skate board. 7.1 – Describing Reactions • Chemical equations are used to describe reactions. – Reactants Products subscript – C + O2 CO2 – The coefficients show the molar ratios of the reactants and products, and they can be changed in order to coefficient balance the equation. – 2Cu + O2 2CuO • Chemical equations are balanced to show that mass is conserved in the chemical reaction. – Only the coefficients, not the subscripts, should change when balancing chemical equations. 7.1 – Balancing Chemical Equations • Step 1 – count the number of atoms of each element on each side of the equation. • Step 2 – change one or more coefficients until the equation is balanced. – Start by balancing an element that appears in only one reactant and product. – Once one element is balanced, proceed to balance another, and another, until all elements are balanced. – Balance chemical formulas by placing coefficients in front of them. Do not add subscripts, because this will change the formulas. – Coefficients are multipliers, so if we write 2 H2O it denotes 2x2=4 hydrogen atoms and 2x1=2 oxygen atoms. 7.1 – Describing Reactions • Chemists use the mole, which is an amount containing 6.02 x 1023 particles, to count large numbers of small particles. – Also known as Avogadro’s number. • The mass of one mole of a substance is called a molar mass. – The molar mass of an element is the same as its atomic mass expressed in grams. – A compound’s molar mass is the sum of the atomic masses of its component elements expressed in grams. 7.1 – Describing Reactions • Molar mass is used to convert between molar and mass amounts of one substance. • A mole ratio is used to convert between molar amounts of two different substances in a chemical reaction. Models of Reactions • The following drawings represent reactants and products of three different chemical reactions. Reaction A reactant products reactants product reactants products Reaction B Reaction C Models of Reactions • 1. Synthesis means “putting something together”. Which drawing represents a synthesis reaction? – Reaction B • 2. Decomposition means “taking something apart”. Which drawing represents a decomposition reaction? – Reaction A • 3. Replacement means “something taking the place of the other”. Which drawing represents a replacement reaction? – Reaction C 7.2 – Types of Reactions • Synthesis reaction – two or more substances react to form a single substance. – “putting something together” – A+B AB – 2Na + Cl2 2NaCl • Decomposition reaction – a single substance reacts to form two or more substances. – – – – “taking something apart” AB A+B 2H2O 2H2 + O2 reverse of synthesis reaction 7.2 – Types of Reactions • Single replacement reaction – one element takes the place of another element in a compound. – A + BC B + AC – Cu + 2AgNO3 2Ag + Cu(NO3)2 • Double replacement reaction – two different compounds exchange positive ions and form two new compounds. – AB + CD AD + CB – CaCO3 + 2HCl CaCl2 + H2CO3 7.2 – Types of Reactions • Combustion reaction – a substance reacts rapidly with oxygen, often generating light and heat. – CH4 + 2O2 – 2H2 + O2 CO2 + 2H2O 2H2O • Oxidation-reduction (redox) reaction – any reaction that involves a transfer of electrons. – 2Ca + O2 • Ca • O + 2e 2CaO 2+ Ca + 2e O2 7.3 – Energy Changes in Reactions • During a chemical reaction, chemical bonds in the reactants are broken and chemical bonds in the products are formed. – Breaking bonds requires energy. – Forming bonds releases energy. • A chemical reaction can be classified as: – Exothermic (releases energy to the surroundings) – Endothermic (absorbs energy from the surroundings) • Energy is conserved during chemical reactions. – Total amount of energy before and after the reaction is the same. 7.4 – Reaction Rates • Reaction rate – the time-rate at which reactants change into products. • Reaction rates are generally increased by the following: – Rise in temperature – Increased surface area – Concentration of reactants, agitation, and catalysts 7.5 – Equilibrium • Equilibrium – when there is no change in the concentrations of reactants and products, and reactants and products are forming simultaneously. – Can only take place when the forward and reverse reactions occur at the same rate. – Products Reactants • Equilibrium can also by physical in nature. – Example: liquid water and water vapor inside a closed container. • Factors affecting chemical equilibrium include: – Shifts in temperature, pressure, and concentration.