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Practice Problem: Combustion Reaction How many grams of products are formed during the combustion of 100. g of ethanol? (and how much oxygen is consumed)?

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Overview of Alkali Metals:
The alkali metals (group 1A) have ns1 outer electron configurations.
- Form +1 cation to “achieve” noble gas configuration.
The reactions of the alkali metals with nonmetals are vigorous.
Common reaction for alkali metals (M) is with halogens (X)
- 2 M + X2 → 2 MX
- Example: 2 Na(s) + Cl2(g) → 2 NaCl(s)
The alkali metals react vigorously with water to form the dissolved alkali metal ion, the hydroxide ion, and hydrogen gas:
- 2 M(s) + 2 H2O(l) → 2 M+(aq) + 2 OH–(aq) + H2(g)
- The reaction is highly exothermic and can be explosive because the heat from the reaction can ignite the hydrogen gas.

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Halogen Overview:
Group 7 elements that have ns2np5 outer electron configurations:
- Mostly form –1 anions (F only forms –1 anion) to achieve the “noble gas configuration”
- Most reactive of the nonmetal elements
The halogens (X) tend to react with metals especially with Group 1 and 2A metals to form ionic compounds such as metal halides (MXn).
- 2 M + n X2 → 2 MXn
- Example: 2 Fe(s) + 3 Cl2(g) → 2 FeCl3(s)
The halogens react with hydrogen to form hydrogen halides.
- H2( g) + X2 → 2 HX(g)

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When table salt is mixed with water, it seems to disappear or become a liquid, and the mixture is homogeneous.
- The salt is still there, as you can tell from the taste or simply boiling away the water.
Homogeneous mixtures are called solutions.
The component of the solution that changes state is called the solute.
The component that keeps its state is called the solvent.

A (not so) common way to express a solution concentration is molality (M).
- Molality is the amount of solute (in moles) divided by the mass of solvent (in kg). CH102

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A common way to express a solution concentration is molarity (M).
- Molarity is the amount of solute (in moles) divided by the volume of solution (in liters).

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The molarity of a solution can be used as a conversion factor between moles of the solute and liters of the solution.
- For example: A 0.500 M NaCl solution contains 0.500 mol NaCl for every liter of solution.

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What is the molarity of a solution made by dissolving 25.5 g of KBr in enough water to give 1.75 L of solution?

Audio 0:34:48.656203 How many liters of a 0.125 M NaOH solution contain 0.255 mol of NaOH?

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A dilution is when a new solution is prepared from a stock solution (more concentrated solution).
To make solutions of lower concentrations from these stock solutions, more solvent is added.
- The amount of solute doesn’t change; just the volume of solution changes:
  - moles solute in solution 1 = moles solute in solution 2
  - The concentrations and volumes of the stock and new solutions are inversely proportional.
The mathematical relationship is C1·V1 = C2·V2, or if the concentration unit is Molarity, then it can be written as M1·V1 = M2·V2.

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What is the concentration of HCl in the final solution when 65 mL of a 9.0 M HCl solution is diluted with pure water to a total volume of .15 L?
- A) 2.1 × 10-2 M
- B) 3.9 M
- C) 21 M
- D) 3.9 × 10^3 M

Term	Definition
solution	homogeneous mixtures
solute	component of solution which changes state
dilute solutions	solutions which have a small amount of solute compared to solvent
molarity	amount of solute (in moles) divided by the volume of solution (in liters)