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C12H22O11 is sucrose (table sugar).
For a 0.10 M solution, KCl is approximately 98% dissociated while CH3CO2H (acetic acid) is a little more than 1% dissociated. The size of the arrows indicate which side of the chemical equation the equilibrium lies on. The use of the equilibrium arrows is minimal until later chapters on kinetics and chemical equilibrium.
Strong acids are strong electrolytes (which is why they are called strong acids!). These are typically called the 6 common strong acids. There are other strong acids.
Hydroxides are also ionic compounds.
Any acid that’s not a strong acid is considered to be a weak acid.
Any molecular compounds which are not already classified (acids are molecular). While water does dissociate to a small degree, we consider it to be a nonelectrolyte. The dissociation of water will be dealt with in a later chapter.
Granted, all of the substances in the chemical equation are ionic compounds but it’s common to call this the molecular equation. Pictures are useful especially with this reaction. Solutions of lead(II) nitrate and potassium iodide are colorless while the precipitate of lead(II) iodide is yellow.
Note the proper charges (as learned previously when writing ionic compound formulas).
This doesn’t suggest that you can actually have a solution of iodide ion. The corresponding cations and anions are present but they are spectator ions. An aqueous solution that contains lead(II) ion when mixed with another one that contains iodide ion will typically produce a precipitate of lead(II) iodide.
Swap the cations to determine the possible products.
Properly written products! Not: AgCO3 and Na2NO3.
Watch the coefficients and subscripts.
“HA” is a generic chemical formula for an acid.
Hydrogen ions do not exist in water. They are attached to one or more water molecules (often in clusters).
For convenience, we’ll write it as hydrogen ion instead of hydronium ion until a later chapter when a deeper look at acids and bases is undertaken.
“M” is shorthand for a metal cation.
It’s really not proper to call “aqueous ammonia” “ammonium hydroxide” even though it’s still commonly labeled as such (ordering chemicals, etc.).
Recall the original definition of an acid-base neutralization written earlier. While it looks goofy to write water as HOH, it can help students remember where the pieces came from: H (acid) and OH (base). It’s also easier to balance.
The order the products are written in is irrelevant.
The products will be water and a salt.
The salt is written using the rules for naming ionic compounds as previously used.
HBr is one of the 6 strong acids.
HF is a weak acid. Since it dissociates only to a small degree in solution, it is not dissociated in the ionic equation.
This is why charges are supposed to be written as “1-”. The corresponding oxidation number is written “-1”.
H bonded to a nonmetal has an oxidation number of +1.
H bonded to a metal has an oxidation number of -1.
In peroxides, O22-, oxygen has an oxidation number of -1.
A major exception is when the halogen is bonded to oxygen.
An “agent” causes something to happen.
These are net ionic equations. The spectator ions (nitrate, for one example) are not involved in the main reaction.
This is a nice one to do as a demonstration. Place a coil of copper wire in a solution of silver nitrate at the beginning of lecture or lab and show it to the students. Show it again at the end of the period.
This is a nice one to do as a demonstration. Place a coil of copper wire in a solution of silver nitrate at the beginning of lecture or lab and show it to the students. Show it again at the end of the period.
Redox reactions can be too difficult to balance by inspection (as in Ch. 3). The oxidation-number method focuses more on the chemical changes by analyzing species which are changing their oxidation numbers.
2 Cr+3 ions: 2(-3)=-6
Do an atom check and a charge balance check at the end.
The half-reaction method focuses on the individual half-reactions which is important for electrochemistry.
LEO says GER. Think of the lion…
Nothing to do since the number of electrons is the same for each half-reaction.
The net ionic equation is shown.
Potassium permanganate is dark purple. As it’s added to a solution of oxalic acid, the permanganate reacts to form Mn2+ and remains colorless (dilute solutions of Mn2+ are colored but it can be difficult to see). When a slight excess of permanganate is added, the solution turns faint purple.
4 significant figures are used in the molar mass since the mass is given to 4 significant figures.