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CHE 1301 Ch 3 Chemical Compounds Part 2 Answers

CHE 1301 Ch 3 Chemical Compounds Part 2 Answers - CHE 1301...

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CHE 1301 Ch 3 Chemical Compounds (2) – Nomenclature ANSWERS Naming Chemical Compounds ANSWERS (See also Examples 3-8 through 3-11, pg 86-90 Petrucci) NOTE: The basic idea here is that we should be able to take the name of a compound and write it’s formula out, or vice versa. For ionic compounds we write formulae in which there is an overall neutral charge, meaning that we balance the charges of the cations(+) and anions(–) to give an overall charge of zero. Monoatomic cations take the name of the parent element. Polyatomics: In general, anything with –ate or –ite at the end has oxygen in it; the ‘ates’ have more oxygen atoms than the ‘ites’. Be aware of the ‘hypo-ite’, ‘ite’, ‘ate’ and ‘per-ate’ series for the oxyanions of chlorine – this can be applied to bromine and iodine also. Note Hydrogen carbonate vs Carbonate – the addition of a hydrogen atom is often seen and the nomenclature usually follows the simple rule of adding ‘hydrogen’ to the start of the name and reducing the negative charge on the anion by one. For oxyacids (compounds formed between hydrogen and an oxyanion) the ending of the acid name is derived from the ending of the oxyanion name (‘ate’ gives ‘ic’, ‘ite’ gives ‘ous’). Note that we only use the prefix hydro- when dealing with binary acids (hydrogen and another non-metal). For acids in general – these are compounds formed between hydrogen and something else. The ‘H’ (or H’s) is written first and the compound will be in water (it will have an (aq)). PLEASE be methodical in this – use the flowcharts I pasted into the summary sections of the lecture slides for you if necessary. Nomenclature can only be mastered through practice and repetition. Write names for the following compounds: NI3 Nitrogen Triiodide (Non-metal + Non-metal) we use the system of prefixes to indicate numbers of atoms of each element. We assume ‘mono’ for the first element of necessary. The second element is named as if it’s an anion (takes –ide ending)). Her we have one nitrogen (written first, therefore we drop the ‘mono’) and three iodine atoms, therefore tri-iodide. FeCl3 Iron (III) Chloride (Transition metal non-metal). We have a metal + non-metal compound, so it’s going to be ionic. In this case, our metal is a transition metal (‘B’ group metal on the periodic table), and so it can have different cation charges. We must, therefore, use the Stock system to indicate the cation charge (roman numeral in brackets after the parent element name). To find the charge on the cation, we looking at what it’s combined with. Here we have three chloride ions, which are always 1– each (chlorine in group 7A has a negative charge equal to 8 minus the group number), hence a total anionic charge of 3–. To make a neutral compound, we must have Fe3+.
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