Reactions in Water or Aqueous Solution

Reactions in Water or Aqueous Solution Several types of reactions occur in water. When water is the solvent for a reaction, the reaction is said to occur in aqueous solution, which is denoted by the abbreviation (aq) following the name of a chemical species in a reaction. Three important types of reactions in water are precipitation, acid-base, and oxidation-reduction reactions. Precipitation Reactions In a precipitation reaction, an anion and a cation contact each other and an insoluble ionic compound precipitate out of solution. For example, when aqueous solutions of silver nitrate, AgNO3, and salt, NaCl, are mixed, the Ag and Cl- combine to yield a white precipitate of silver chloride, AgCl: Ag(aq) Cl-(aq) → AgCl(s) Acid-Base Reactions For example, when hydrochloric acid, HCl, and sodium hydroxide, NaOH, are mixed, the H reacts with the OH- to form water: H(aq) OH-(aq) → H2O HCl acts as an acid by donating H ions or protons and NaOH acts as a base, furnishing OH- ions. Oxidation-Reduction Reactions In an oxidation-reduction or redox reaction, there is an exchange of electrons between two reactants. The species that loses electrons is said to be oxidized. The species that gains electrons are said to be reduced. An example of a redox reaction occurs between a hydrochloric acid and zinc metal, where the Zn atoms lose electrons and are oxidized to form Zn2 ions: Zn(s) → Zn2(aq) 2e- The H ions of the HCl gain electrons and are reduced to H atoms, which combine to form H2 molecules: 2H(aq) 2e- → H2(g) The overall equation for the reaction becomes: Zn(s) 2H(aq) → Zn2(aq) H2(g) Two important principles apply when writing balanced equations for reactions between species in a solution: The balanced equation only includes the species that participate in forming products. For example, in the reaction between AgNO3 and NaCl, the NO3- and Na ions were not involved in the precipitation reaction and were not included in the balanced equation.The total charge must be the same on both sides of a balanced equation. Note that the total charge can be zero or non-zero, as long as it is the same on both the reactants and products sides of the equation.

Cover Letter Guide Writing Your Best Cover Letter for 2017

Cover Letter Guide Writing Your Best Cover Letter for 2017 The cover letter is often the underappreciated sibling of the resume. It’s a little lefts)Do You Have Tips for My Particular Field?Here at TheJobNetwork, we’re constantly working on spotlighting different fields, but if you’re in one of these fields and writing a cover letter, then you are already in luck:How to Write a Perfect Teacher Cover LetterHow to Write a Perfect Admin Assistant Cover LetterHow to Write a Perfect Human Resources Cover LetterEven if you’re not in one of these specific fields, you’ll find helpful tips and tricks that you can apply to your own letter as well.And there you have it†¦you should be good to start your own cover letter! Congrats on not neglecting this oft-overshadowed piece of your applicant package, and boosting your chances of getting to the next steps.