Chapter 4 Flashcards
What are acids?
- Species that release H+ ions in solutions
What are bases?
- Substances that readily accept H+ ions (from acids)
What are alkalis?
- Bases that release hydroxide ions in solutions
What are strong acids?
- Acids that dissociate completely in solution
What are weak acids?
- Acids that only dissociate partially in solution
List 3 strong acids.
- Hydrochloric acid (HCl)
- Nitric acid (HNO3)
- Sulfuric acid (H2SO4)
Which types of acids tend to be weak acids? Give an example.
- Organic acids
- Ethanoic acid (CH3COOH)
How are the salts formed from carboxylic acids named?
- After their stem (e.g. meth, eth, etc.) add ‘anoate’
- E.g. sodium ethanoate
What is neutralisation?
- A reaction of:
- H+ and OH- to form water
- acids and bases
How do acids and metal oxides react together?
- Acids + metal oxides -> salt + water
How do acids and metal hydroxides react together?
- Acids + metal hydroxides -> salt + water
How do acids and metal carbonates react together?
- Acids + metal carbonate -> salt + water + carbon dioxide
What 3 things can titrations be used for?
- Finding the concentration of a solution
- Identifying unknown chemicals
- Finding the purity of a substance
What is a standard solution?
- A solution of known concentration
How do you prepare a standard solution?
- The solid is weighed accurately.
- It is dissolved in a beaker using less distilled water than needed to fill the volumetric flask to the graduation line.
- The solution is transferred to a 250cm^3 volumetric flask. The last traces of the solution are rinsed into the flask with distilled water.
- The flask is filled to the graduation line using distilled water a drop at a time, until the bottom of the meniscus lines up exactly with the mark when viewed at eye level from the mark.
- A stopper is put on the volumetric flask, and it is then inverted several times to mix the solution thoroughly.
What are 2 common errors when creating a standard solution, and what impact do they have?
- Too much water is added; the solution is too dilute
- The flask is not inverted; the concentration is not consistent, so neither will the titration results be
What are concordant results? How are they used?
- Results within 0.1cm^3 of each other
- Titrations are repeated until you obtain concordant results, which are then used to calculate the mean titre, to prevent accuracy from being lost
What is an oxidation number?
- A measure of the number of electrons that an atom uses to bond with atoms of another element
What is an oxidation state?
- The oxidation number
What is the oxidation number of an element, and which situations does this apply to?
- 0
- This includes if it exists as a molecule (such as oxygen)
What is the oxidation number of an ion?
- It is the same as its ionic charge
- However, the sign comes before the number
How do you find the oxidation number of elements in a compound?
- The individual charges added up equal the total charge of the compound
Give an example of an exception when it comes to the oxidation numbers of elements in compounds.
- When a compound contains both Cl and O, Cl may not have the oxidation number -1
What are Roman numerals used for in the name of compounds?
- They show the oxidation state of an element
- They don’t show the sign, but that is clear from the context
What are the 3 different ways of defining oxidation?
- The addition of oxygen
- The loss of electrons
- An increase in oxidation number
What are the 3 different ways of defining reduction?
- The removal of oxygen
- The gain of electrons
- A decrease in oxidation number
