News Match up the formulae Formulae of compounds
- Slides: 20
News! Match up the formulae Formulae of compounds Learning aims: Recognise common formulae Carry out flame tests 1
Formulas of elements and molecules • Individual elements are usually written as A compound when single atoms e. g. Na, is Mg, C, S, Fe more than one are written as • A few non-metallic elements element is chemically molecules containing two atoms: bonded to another • Hydrogen H 2 element • Fluorine F 2 etc. • It is important to be able to recognise common formulae 2
Some common compounds name formula atoms present HCl 1 H + 1 Cl sulphuric acid H 2 SO 4 2 H+1 S+4 O nitric acid HNO 3 1 H+1 N+3 O sodium hydroxide Na. OH 1 Na + 1 O + 1 H KOH 1 K+1 O+1 H carbon monoxide CO 1 C+1 O carbon dioxide CO 2 1 C+2 O ammonia NH 3 1 N + 3 H nitrogen dioxide NO 2 1 N+2 O sulphur dioxide SO 2 1 S+2 O sulphur trioxide SO 3 1 S+3 O hydrochloric acid potassium hydroxide 3
Have a read! The valency is the combining power of an element Think of the positive charged Take a few minutes to read pages 2 and 3 of your worksheet valencies as the to look at common valencies of ions first name, and the negatively charged A positive valency as the surname, ion or atom, will when naming a combine with a compound. negatively charged one 4
How do we go about writing the formula • • • Write down the symbols from the table List the valency below each Cross them over Cancel them down if possible Write the formulae Let’s work through some examples… 5
Formula of compounds sodium oxide symbols Na O valency 1 2 formula Na 2 O 6
Formula of compounds lithium nitrate symbols Li NO 3 valency 1 1 formula Li. NO 3 7
Formula of compounds copper(II) nitrate symbols Cu NO 3 valency 2 1 formula Cu(NO 3)2 8
Formula of compounds chromium(III) oxide symbols Cr O valency 3 2 formula Cr 2 O 3 9
Formula of compounds ammonium sulphate symbols NH 4 SO 4 valency 1 2 formula (NH 4)2 SO 4 10
Formula of compounds iron(II) hydroxide symbols Fe OH valency 2 1 formula Fe(OH)2 11
Formula of compounds 1 Nickel(II) iodate(V) Ni(IO 3)2 Magnesium carbonate Mg. CO 3 Potassium hydrogencarbonate KHCO 3 Copper(II) sulphate Cu. SO 4 Magnesium nitride Mg 3 N 2 Zinc iodide Zn. I 2
Formula of compounds 2 Barium sulphite Ba. SO 3 Lead(II) sulphate Mg. SO 4 Sodium hydrogensulphate Na. HSO 4 Aluminium chloride Al. Cl 3 Chromium(III) nitrate Cr(NO 3)3 Iron(II) bromide Fe. Br 2 13
Formula of compounds 3 Silicon chloride Si. Cl 4 Ammonium phosphate (NH 4)3 PO 4 Silver dichromate(VI) Ag 2 Cr 2 O 7 Iron(III) oxide Fe 2 O 3 Sodium nitrite Na. NO 2 Potassium manganate(VII) KMn. O 4 14
Break 15
Qualitative analysis q. Qualitative analysis is a method of analysis that tells us whether a substance is present or not. q. It does not tell us how much of something is there, so no numerical values q. Qualitative analysis of metal ions – flame tests q. Qualitative analysis of salts 16
Flame tests • When metals or salts containing those metals are heated in a flame characteristic colours are produced. This is used to identify certain metals. 17
Demo! 18
Flame tests Safety First: Wear safety goggles Stand up Tuck your chair & bags under your desk Tie back long hair 19
Formulae of compounds Learning aims: Recognise common formulae Carry out flame tests 20
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