- What are strong and weak electrolytes?
- Differences
- Methods to identify electrolytes
- Examples of strong and weak electrolytes
- Strong electrolytes
- Strong acids:
- Strong bases
- Strong salts
- Weak electrolytes
- Weak acids
- Weak bases and nitrogen compounds
- References
The electrolytes are substances that produce a conductive solution to the dissolved electricity be in a polar solvent such as water. The dissolved electrolyte separates into cations and anions, which are dispersed in said solution. If an electric potential is applied to the solution, the cations will adhere to the electrode that has an abundance of electrons.
Instead, the anions in the solution will bind to the electron-deficient electrode. A substance that dissociates into ions acquires the ability to conduct electricity. Most soluble salts, acids, and bases represent electrolytes.
Some gases, such as hydrogen chloride, can act as electrolytes at certain conditions of temperature and pressure. Sodium, potassium, chloride, calcium, magnesium, and phosphate are good examples of electrolytes.
What are strong and weak electrolytes?
The strong electrolytes are those which ionize completely, that is, separate to 100% - while the weak electrolyte only partially ionize. This percentage of ionization is usually around 1 to 10%.
To better differentiate these two types of electrolytes, it can be said that in the solution of a strong electrolyte the main species (or species) are the resulting ions, while in the solution of weak electrolytes the main species is the compound itself without ionize.
Strong electrolytes fall into three categories: strong acids, strong bases, and salts; while weak electrolytes are divided into weak acids and weak bases.
All ionic compounds are strong electrolytes, because they separate into ions when dissolved in water.
Even the most insoluble ionic compounds (AgCl, PbSO 4, CaCO 3) are strong electrolytes, because the small amounts that do dissolve in water do so mainly in the form of ions; that is, there is no dissociated form or amount of the compound in the resulting solution.
The equivalent conductivity of electrolytes decreases at higher temperatures, but they behave in different ways depending on their strength.
Strong electrolytes show less decrease in conductivity at higher concentration, while weak electrolytes have a large rate of decrease in conductivity at higher concentration.
Differences
It is important to know how to recognize a formula and recognize in which classification it is found (ion or compound), because the safety regulations will depend on this when working with chemicals.
As stated above, electrolytes can be identified as strong or weak based on their ionization capacity, but this can sometimes be more obvious than it seems.
Most soluble acids, bases, and salts that do not represent weak acids or bases are considered weak electrolytes.
In fact, it must be assumed that all salts are strong electrolytes. In contrast, weak acids and bases, in addition to nitrogen-containing compounds, are considered weak electrolytes.
Methods to identify electrolytes
There are methods to facilitate the identification of electrolytes. Here is a six-step method:
- Is your electrolyte one of the seven strong acids?
- Is it in the metal (OH) n form ? So it is a strong base.
- Is it in the metal (X) n form ? Then it is a salt.
- Does your formula start with an H? So it's probably a weak acid.
- Does it have a nitrogen atom? So it may be a weak base.
- None of the above apply? So it is not an electrolyte.
Furthermore, if the reaction presented by the electrolyte looks like the following: NaCl (s) → Na + (aq) + Cl - (aq), in which the reaction is delimited by a direct reaction (→), we are talking of a strong electrolyte. If it is delimited by an indirect (↔) it is a weak electrolyte.
As stated in the previous section, the conductivity of an electrolyte varies according to its concentration in the solution, but this value also depends on the strength of the electrolyte.
At higher concentrations, the strong and intermediate electrolytes will not decrease in significant intervals, but the weak ones will show a high decrease until reaching values close to zero at higher concentrations.
There are also intermediate electrolytes, which can dissociate in solutions at higher percentages (less than 100% but greater than 10%), in addition to non-electrolytes, which simply do not dissociate (carbon compounds such as sugars, fats and alcohols).
Examples of strong and weak electrolytes
Strong electrolytes
Strong acids:
- Perchloric acid (HClO 4)
- Hydrobromic acid (HBr)
- Hydrochloric acid (HCl)
- Sulfuric acid (H 2 SO 4)
- Nitric acid (HNO 3)
- Periodic acid (HIO 4)
- Fluoroantimonic acid (HSbF 6)
- Magic acid (SbF 5)
- Fluorosulfuric acid (FSO 3 H)
Strong bases
- Lithium hydroxide (LiOH)
- Sodium hydroxide (NaOH)
- Potassium hydroxide (KOH)
- Rubidium hydroxide (RbOH)
- Cesium hydroxide (CsOH)
- Calcium hydroxide (Ca (OH) 2)
- Strontium hydroxide (Sr (OH) 2)
- Barium hydroxide (Ba (OH) 2)
- Sodium amide (NaNH 2)
Strong salts
- Sodium chloride (NaCl)
- Potassium nitrate (KNO 3)
- Magnesium Chloride (MgCl 2)
- Sodium acetate (CH 3 COONa)
Weak electrolytes
Weak acids
- Acetic acid (CH 3 COOH)
- Benzoic acid (C 6 H 5 COOH)
- Formic acid (HCOOH)
- Hydrocyanic acid (HCN)
- Chloroacetic acid (CH 2 ClOOH)
- Iodic acid (HIO 3)
- Nitrous acid (HNO 2)
- Carbonic acid (H 2 CO 3)
- Phosphoric acid (H 3 PO 4)
- Sulfurous acid (H 2 SO 3)
Weak bases and nitrogen compounds
- Dimethylamine ((CH 3) 2 NH)
- Ethylamine (C 2 H 5 NH 2)
- Ammonia (NH 3)
- Hydroxylamine (NH 2 OH)
- Pyridine (C 5 H 5 N)
- Aniline (C 6 H 5 NH 2)
References
- Strong electrolyte. Retrieved from en.wikipedia.org
- Anne Helmenstine, P. (nd). Science Notes. Retrieved from sciencenotes.org
- OpenCourseWare. (sf). UMass Boston. Retrieved from ocw.umb.edu
- Chemistry, D. o. (sf). St. Olaf College. Retrieved from stolaf.edu
- Anne Marie Helmenstine, P. (nd). ThoughtCo. Retrieved from thoughtco.com