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fandomhigh2006-02-07 10:12 am
equalsmcsquared.livejournal.com) wrote in fandomhigh2006-02-07 10:12 am
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Chemistry (4th Period)
"Good morning. Today we will begin discussing the mathematics behind chemistry."
In chemistry, we use symbols to represent the various chemicals. Success in chemistry depends upon developing a strong familiarity with these basic symbols. For example, the symbol "C" represents an atom of carbon, and "H" represents an atom of hydrogen. To represent a molecule of table salt, sodium chloride, we would use the notation "NaCl", where "Na" represents sodium and "Cl" represents chlorine. We call chlorine "chloride" in this case because of its connection to sodium. You should have reviewed naming schemes, or nomenclature, in earlier readings.
A chemical equation is an expression of a chemical process. For example:
AgNO3(aq) + NaCl(aq) ---> AgCl (s) + NaNO3(aq)
In this equation, AgNO3 is mixed with NaCl. The equation shows that the reactants (AgNO3 and NaCl) react through some process (--->) to form the products (AgCl and NaNO3). Since they undergo a chemical process, they are changed fundamentally.
Often chemical equations are written showing the state that each substance is in. The (s) sign means that t he compound is a solid. The (l) sign means the substance is a liquid. The (aq) sign stands for aqueous in water and means the compound is dissolved in water. Finally, the (g) sign mean s that the compound is a gas.
Coefficients are used in all chemical equations to show the relative amounts of each substance present. This amount can represent either the relative number of molecules, or the relative number of moles (described below). If no coefficient is shown, a one (1) is assumed.
On some occasions, a variety of information will be written above or below the arrows. This information, such as a value for temperature, shows what conditions need to be present for a reaction to occur. For example, in the graphic below, the notation above and below the arrows shows that we need a chemical Fe2O3, a temperature of 1000 degrees C, and a pressure of 500 atmospheres for this reaction to occur.
Given the equation above, we can tell the number of moles of reactants and products. A mole simply represents Avogadro's number (6.023 x 1023) of molecules. A mole is similar to a term like a dozen. If you have a dozen carrots, you have twelve of them. Similarily, if you have a mole of carrots, you have 6.023 x 1023 carrots. In the equation above there are no numbers in front of the terms, so each coefficient is assumed to be one (1). Thus, you have the same number of moles of Ag NO3, NaCl, AgCl, NaNO3.
Converting between moles and grams of a substance is often important. This conversion can be easily done when the atomic and/or molecular weights of the substance(s) are known. Given the atomic or molecular weight of a substance, that mass in grams makes a mole of the substance. For example, calcium has an atomic weight of 40 atomic mass units. So, 40 grams of calcium makes one mole, 80 grams makes two moles, etc.
"Your homework is to work the problems at the end of the fifth chapter in your textbooks. On Thursday, we will learn how to balance equations. Have a good day."
In chemistry, we use symbols to represent the various chemicals. Success in chemistry depends upon developing a strong familiarity with these basic symbols. For example, the symbol "C" represents an atom of carbon, and "H" represents an atom of hydrogen. To represent a molecule of table salt, sodium chloride, we would use the notation "NaCl", where "Na" represents sodium and "Cl" represents chlorine. We call chlorine "chloride" in this case because of its connection to sodium. You should have reviewed naming schemes, or nomenclature, in earlier readings.
A chemical equation is an expression of a chemical process. For example:
AgNO3(aq) + NaCl(aq) ---> AgCl (s) + NaNO3(aq)
In this equation, AgNO3 is mixed with NaCl. The equation shows that the reactants (AgNO3 and NaCl) react through some process (--->) to form the products (AgCl and NaNO3). Since they undergo a chemical process, they are changed fundamentally.
Often chemical equations are written showing the state that each substance is in. The (s) sign means that t he compound is a solid. The (l) sign means the substance is a liquid. The (aq) sign stands for aqueous in water and means the compound is dissolved in water. Finally, the (g) sign mean s that the compound is a gas.
Coefficients are used in all chemical equations to show the relative amounts of each substance present. This amount can represent either the relative number of molecules, or the relative number of moles (described below). If no coefficient is shown, a one (1) is assumed.
On some occasions, a variety of information will be written above or below the arrows. This information, such as a value for temperature, shows what conditions need to be present for a reaction to occur. For example, in the graphic below, the notation above and below the arrows shows that we need a chemical Fe2O3, a temperature of 1000 degrees C, and a pressure of 500 atmospheres for this reaction to occur.
Given the equation above, we can tell the number of moles of reactants and products. A mole simply represents Avogadro's number (6.023 x 1023) of molecules. A mole is similar to a term like a dozen. If you have a dozen carrots, you have twelve of them. Similarily, if you have a mole of carrots, you have 6.023 x 1023 carrots. In the equation above there are no numbers in front of the terms, so each coefficient is assumed to be one (1). Thus, you have the same number of moles of Ag NO3, NaCl, AgCl, NaNO3.
Converting between moles and grams of a substance is often important. This conversion can be easily done when the atomic and/or molecular weights of the substance(s) are known. Given the atomic or molecular weight of a substance, that mass in grams makes a mole of the substance. For example, calcium has an atomic weight of 40 atomic mass units. So, 40 grams of calcium makes one mole, 80 grams makes two moles, etc.
"Your homework is to work the problems at the end of the fifth chapter in your textbooks. On Thursday, we will learn how to balance equations. Have a good day."