Since we have information about temperature and we are interested in changes in pessure, Gay-Lussac's Law will be used. This says that

The initial temperature and pressure are given (STP) meaning a temperature of  and a pressure of . There are other values for standard pressure but they have different units and since the problems requests an answer in units of  we must use the value of standard pressure with those units. Solving for the final pressure gives

Plugging in our variables gives

We want 3 significant figures since the temperature given has 3, so the final answer is

Since pressure is kept constant, we can directly compare the moles of gas in the container and volume using Avogadro's law. Since moles of gas and volume are on opposite sides of the ideal gas law, the two variables are directly proportional to one another.

Avogadro's law is written as follows:

First, we will need to convert the initial mass of gas to moles. It is important to remember that nitrogen gas is diatomic!

Use this value and the given volumes to solve for the final amount of gas in the container.

Avogadro's Law states that two gases at the same temperature and volume will have an equal number of molecules, and therefore the same number of moles.

It does not matter that helium has one atom per molecule while carbon tetrachloride has five atoms per molecule. Note that the given volume per mole of gas at STP is standard, and true for any gas. At STP, one mole of gas will always have a volume of 22.5L, regardless of its identity.

To find the number of neutrons, we must convert the moles to atoms by multiplying the moles by Avogadro's number .

Now looking at the periodic table, the neutrons per atom can be found by subtracting the atomic weight by the atomic number:

Thus there are 14 neutrons in each atom of aluminum.

There are three principle definitions for acids and bases.

The Arrhenius definition is the simplest, and states that acids are compounds that increase proton concentration in solution, while bases are compounds that increase hydroxide concentration in solution. Arrhenius acids will always contain hydrogen and Arrhenius bases will always contain hydroxide groups.

Brønsted-Lowry definitions center on proton donation. Brønsted-Lowry acids are species that donate protons, and Brønsted-Lowry bases are compounds that accept protons.

Lewis acids and bases refer to the donation or acceptance of an electron pair. Lewis bases donate an electron pair, and Lewis acids accept an electron pair.

An acidic solution will always have a hydronium concentration greater than . A basic solution will always have a hydroxide concentration greater than . If the hydroxide concentration is equal to the hydronium concentration, the solution is neutral.

The opposite of the above conditions can also be noted. If the hydronium concentration is less than , then the solution will be basic. An example of this is a solution where the hydronium ion concentration is . Since this value is far less than , this will be a basic solution.

Strong acids and bases dissociate completely into ions when placed in an aqueous solution. In contrast, weak acids and bases do not completely dissociate.

There are only six strong acids: perchloric acid (HClO₄), hydroiodic acid (HI), hydrobromic acid (HBr), hydrochloric acid (HCl), nitric acid (HNO₃), and sulfuric acid (H₂SO₄).

There are three primary classifications of acids and bases.

Arrhenius acids yield protons when dissolved in solution, while Arrhenius bases yield hydroxide ions.

Brønsted-Lowry acids are protone donors, while Brønsted-Lowry bases are proton acceptors.

Lewis acids are electron acceptors, while Lewis bases are electron donors.

An acid that dissociates completely in solution is considered a strong acid due to its high Ka value.

The most common Lewis bases are anions, and therefore, have unpaired valence electrons which may be donated to Lewis acids. The concept of donating and/or accepting hydrogens refers to the Bronsted-Lowry definition of acids. A Bronsted-Lowry acid donates hydrogens.

Acids are soluble in water substance, but remember, only water gets the liquid (l) phase label. Since acids are almost always dissolved in water, we use the (aq) subscript at the end of the chemical formula to indicate its phase.