EasyChemistryHigh School (9–10)GeneralAtoms and Molecules › Molecules, Ions and FormulaeConceptualBoard Exam
Write the formula of each compound. Use the valencies: Na, K and NH₄ are 1; Mg and Ca are 2; CO₃…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Write the formula of each compound. Use the valencies: Na, K and are ; Mg and Ca are ; and are ; OH is .
- Potassium sulphate
- Ammonium carbonate
- Magnesium hydroxide
- Calcium sulphate
- Sodium carbonate
Need a reminder? The key ideaShow
Valency is the combining capacity of an atom or group. Criss-cross: write the symbols and valencies, cross the valencies over, simplify, and put a group in a bracket if there is more than one of it. Names: the metal first, then the non-metal ending in ide, or the group's name.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) . (b) . (c) .
Step 2. (d) Crossing and gives , which simplifies to . (e) .
Answer: , , , , .
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