|Dissociation||Single Replacement||Double Replacement|
|Molecular vs. Empirical formula||Significant Digits||Percent Yields|
|Units of Pressure||Chemistry Laws||Solids, Liquids, Gases compared|
A combustion reaction is when all substances in a compound are combined with oxygen, which then produces carbon dioxide and water. Combustion is commonly called burning. It is an exothermic reaction, which means heat is produced and is easily distinguished. Combustion occurs predominantly in automobiles, homes, and in factories. An example of a combustion reaction is as follows:
CxHy + O2 --> CO2 + H2O
A synthesis reaction is when there is a combination of two or more substances and a compound results. An example of a synthesis reaction is as follows:
A + B --> AB
Decomposition is the opposite of synthesis. It is when a compound is broken down into simpler substances, usually through electrolysis. An example of decomposition is as follows:
AB --> A + B
Dissociation is commonly mistaken as decomposition, but there is a difference. When the compound is broken down, it is broken down into ions rather than atoms, so there will be a charge on the product side of the equation. An example of dissociation is as follows:
AB --> A+ + B-
In a single replacement reaction, there is a rule that is always followed. A metal replaces a metal, or a nonmetal replaces a nonmetal. An example of a single replacement reaction is as follows:
A + BC --> AC + B
In a double replacement reaction, this rule is always followed. A metal replaces a metal, and a nonmetal replaces a nonmetal. An example of a double replacement reaction is as follows:
AB + XY --> AY + XB
An empirical formula gives only the simplest whole number ratio of atoms in an ionic formula. A molecular formula is the formula used in a molecular compound. The molecular formula for ethylene is C2H4. The empirical formula for ethylene gives the simplest form, which is CH2.
|Number||Digits to count||Example||Number of Significant Digits|
|Trailing Zeros||Only if decimal point||*400.0* or *4*00||4 or 1|
|Scientific Notation||All||*3.7* X 10-2||2|
Rounding Fives with Significant Digits:
For a 5, even with zeros trailing it, increase the last significant digit (see above) by 1 if the digit preceding the 5 is odd. Do not change the last significant digit if the digit preceding the 5 is even. Take a look at these examples:
3.7500 becomes 3.8
3.6500 becomes 3.6
For a five followed by non-zero digits, just increase the last significant digit by 1.
8.652 becomes 8.7
8.6504 becomes 8.7
Theoretical Yield: The amount of product predicted to form on the basis of the balanced chemical equation.
Actual Yield: The amount of product actually obtained in a reaction.
Percent Yield: Shows efficiency of reaction by comparing results of Theoretical Yield and Actual Yield. To find the Percent Yield, divide the Actual Yield by the Theoretical Yield, and multiply it by 100%.
|Unit||Equivalence of 1 kPa|
|Pascal (Pa)||1 kPa = 1000 Pa|
|Atmosphere (atm)||1 kPa = 0.009 869 atm|
|Bar||1 kPa = 0.01 bar|
|Torr||1 kPa = 7.501 torr|
|Millimeter of mercury (mm Hg)||1 kPa = 7.501 mm Hg|
|Pounds per square inch (psi)||1 kPa = .145 psi|
Ptotal = Pa + Pb + Pc
Gas volume varies with temperature.
In gases, as pressure increases, volume decreases.
Equal volumes of gases (at the same temperature and pressure) contain equal numbers of particles.
PV = nRT
R = 0.08206 L atm/mol K
1 atm, 273 K
22.4 L or 22.4 dm3 at STP
The particles of a solid are always arranged in an orderly manner. They have a constant volume, because the particles are so closely packed together, with very little space between them. Compression of a solid to any large extent is not possible because of this tight pack of particles.
A fluid is any substance that flows, and liquids are examples of fluids. The particles in liquids are allowed to freely move and change their positions. At all times are the particles moving, moving from neighbor to neighbor. This is why we can 'pour' a liquid into another container. A liquids confinement are the borders of its container. This is why when we pour a liquid into another container, there is conformity to the shape of the container. Compression of a liquid to any large extent is not possible.
Gases is another example of a fluid, it flows! The particles of gases are however much different than that of solids and liquids. The particles in gases are not neatly arranged, and they don't even touch each other most of the time. There is lots of space in between particles, which is why when put in a container, it is filled with the gas. And when released from a container, the gas is dispersed. The particles in gases are always moving, just like the particles in a liquid.