chem test - 3/27/24 Flashcards
What is the Law of Conservation of Mass?
Atoms can only be rearranged in a chemical reaction, not created or destroyed, leading to the conservation of mass where the mass of reactants equals the mass of products, only in a closed system.
What are open systems?
Systems that allow matter to enter or leave, potentially altering the total mass while still adhering to the law of conservation.
What are closed systems?
Systems that do not allow matter to enter or leave, maintaining a constant mass according to the law of conservation, though energy may change forms.
What is a synthesis reaction?
Reactions where smaller molecules combine to form larger molecules, represented by A + B → AB.
What is a decomposition reaction?
Reactions where large molecules break down into elements or smaller molecules, represented by AB → A + B.
What is a single displacement reaction?
Reactions where a single element displaces another element in a compound, represented by Z + AB → ZB + A.
Metals can only replace other metals
What is double displacement reaction?
Reactions where elements exchange places within compounds, represented by AB + BC → BB + AC.
What is a combustion reaction?
Reactions where a fuel reacts rapidly with oxygen, producing oxides and energy, potentially resulting in complete or incomplete combustion.
What is an acid?
Aqueous solutions that produce H+ ions, characterized by sour taste, reactivity with metals, and ability to change colors of indicators.
What is a base?
Aqueous solutions that produce OH- or CO32- ions, characterized by bitter taste, slippery feel, and ability to conduct electricity.
What is the pH scale?
Measure of acidity or basicity on a scale from 0 to 14, where pH less than 7 indicates acidity, 7 indicates neutrality, and greater than 7 indicates basicity.
What are acid-base indicators?
Substances that change color based on the acidity or basicity of a solution, such as litmus paper.
What is neutralization?
Reaction between an acid and a base to form water and an ionic compound, resulting in a pH closer to 7.
What happens in neutralization reactions?
Double displacement reactions where acids and bases react to produce water and a salt.
What are the products in complete combustion?
Hydrocarbon + oxygen → carbon dioxide + water + energy
What are the products in incomplete combustion?
Hydrocarbon + oxygen → carbon dioxide + water + carbon monoxide + carbon + energy
What is the difference between rust and corrosion?
Corrosion: Breakdown of a metal as a result of chemical reactions with its environment.
Rusting: One form of corrosion; the corrosion of metals that contain iron.
What causes rust? What prevents it?
Causes: Corrosion of iron affected by air, water, electrolytes, acidity
Prevention: use corrosion resistant materials, such as plastic or paint, protective coating and galvanizing steel.
Corrosion: How does salt contribute to the condition of the car?
It can affect both the bodies of cars and the metal supports of bridges as salt speeds up the process of corrosion once it begins. Salt can create more rust on cars that have already been corroded.
Corrosion: What have car companies done differently from the past to avoid rusting on bumpers?
They have began to make bumpers out of plastic rather than steel as it doesn’t corrode and is much lighter than steel
Corrosion: How does this strategy benefit the environment?
It can reduce the release of metal pollutants and conserve the resources used in steel production that can be very wasteful and harmful
Corrosion: What is meant by beneficial corrosion and how does this differ from rusting?
Beneficial corrosion happens when metals like aluminum or copper develop protective coatings like aluminum oxide or greenish patina, protecting the metal from further damage. In contrast, rusting is the corrosion of iron, where the rust layer doesn’t protect the metal but continues to degrade it.
What is the optimal pH range for swimming pools?
7.2-7.8
What happens if pH drops below this optimal range?
Water irritates the eyes
What chemical can be used to fix pH level drop in swimming pools?
Products containing sodium carbonate can be added to raise the pH when it is too low
What are the compounds causing acid precipitation?
Sulfur dioxide and nitrogen oxides
What are the major sources that produce these compounds in Canada?
Industrial processes like burning coal for electricity generation, smelting metals and vehicle emissions from burning fossil fuels
What are the economical impacts of acid precipitation in Canada?
Damage to forests, steel structures, limestone buildings, stone monuments and losses in wood production and recreational fishing
What are the methods or regulations that help to reduce the emission of the acid precipitation causing compounds in North America?
Switching to low-sulfur fossil fuels, installing scrubbers on smokestacks, improving pollution control equipment on vehicle and enacting stricter anti-pollution laws like Ontario’s Drive Clean Program
Name the properties of bases
bitter taste, slippery feel, 7-14 pH, ionic compounds; ions released when aqueous, good conductors of electricity, water soluble, corrosive
Name the properties of acids
sour taste, water soluble, reacts with metals to release hydrogen gas, reacts with carbonates to release carbon dioxide gas, good conductors of electricity, pH scale of 1-6 (more hydrogen ions released when aqueous = strong acid = low pH)
Acid-base indication (litmus paper)
Red litmus paper:
Turns blue if acidic
Remains red if neutral
Remains red if basic
Blue litmus paper:
Remains blue if acidic
Remains blue if neutral
Turns red if basic
Acid-base indication (bromothymol blue)
Colour in acid = yellow
Colour in base = blue
Acid-base indication (phenolphthalein)
Colourless = acid
Pink = base
Acid-base indication (phenol red)
Yellow = acid
Red/pink = base
Acid-base indication (methyl orange)
Red = acid
Orange/yellow = base
Acid-base indication (cabbage juice)
Red/pink = acid
Green/yellow = base
