Express all quantities in terms of MOLARITY (moles per liter).

In making an ICE chart the following items should be noted:

The oxidation-reduction reaction occuring between iron(III) chloride and tin(II) chloride.

The thermal decomposition of calcium carbonate.

The production of ammonia from nitrogen and hydrogen gases.

When one or more gaseous substances are involved, the K p expression is also given. When one or more of the species in a system exists in the gaseous phase, the partial pressure of that species can be used in the equilibrium expression Dissolved species are still expressed as moles per liter (molarity).Įxamples of equilibrium expressions K c for a variety of equilibrium systems follow. There are two cases when a species is not shown in the equilibrium expression: The 'c' in K c indicates that the value of K is determined using the concentrations of each species. 'a, b, c, and d' represent the coefficients used to balance the equation. The brackets '' represent the concentration of the species (moles per liter or molarity). The general equilibrium expression for a reaction: Then we convert to grams to find the amount of oxygen that needs to be added: Then, because there are five (5) molecules of oxygen to every two (2) molecules of C 2H 2, we need to multiply the result by 5/2 to get the total molecules of oxygen. Therefore we know that 1 mole of C 2H 2 weighs 26 g (2 × 12 grams + 2 × 1 gram). To be able to calculate the moles we need to look at a periodic table and see that 1 mole of C weighs 12.0 g and H weighs 1.0 g. To solve this problem, it is necessary to determine how much oxygen should be added if all of the reactants were used up (this is the way to produce the maximum amount of CO 2).įirst, we calculate the number of moles of C 2H 2 in 6.0 g of C 2H 2. If she uses the equation below, how much oxygen should she add to the reaction?ĢC 2H 2(g) + 5O 2(g) -> 4CO 2(g) + 2 H 2O(l)

Often, it is necessary to identify the limiting reagent in a problem.Įxample: A chemist only has 6.0 grams of C 2H 2 and an unlimited supply of oxygen and he desires to produce as much CO 2 as possible. Sometimes when reactions occur between two or more substances, one reactant runs out before the other.

How many moles of Ca are in 4.50 grams of Ca?Ĭitation: Department of Chemistry at UNC Chapel Hill at Molar Mass of Ca = 40.08 (From the Periodic Table) So, 40 grams of calcium makes one mole, 80 grams makes two moles, etc. For example, calcium has an atomic mass of 40 atomic mass units. Given the atomic or molecular mass of a substance, that mass in grams makes a mole of the substance. This conversion can be easily done when the atomic and/or molecular mass of the substance(s) are known. Thus, you have the same number of moles of AgNO 3, NaCl, AgCl, NaNO 3.Ĭonverting between moles and grams of a substance is often important. In the equation above there are no numbers in front of the terms, so each coefficient is assumed to be one (1). Similarly, if you have a mole of carrots, you have 6.022 x 10 23 carrots.

If you have a dozen carrots, you have twelve of them. A mole is similar to a term like a dozen. Given enough information, one can use stoichiometry to calculate masses, moles, and percents within a chemical equation.Ī mole simply represents Avogadro's number (6.022 x 10 23) of molecules. Stoichiometry is simply the math behind chemistry.

Chemlab notes stoichiometry