EasyChemistryHigh School (9–10)GeneralAtoms and Molecules › Laws of Chemical CombinationConceptualBoard Exam
Which idea of Dalton's atomic theory explains each of these? …
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Which idea of Dalton's atomic theory explains each of these?
- The total mass does not change in a chemical reaction.
- Pure water always has hydrogen and oxygen in the ratio by mass.
- Carbon dioxide always has one carbon atom for every two oxygen atoms.
Need a reminder? The key ideaShow
Dalton: matter is made of atoms, which are not created or destroyed in a reaction; atoms of one element are alike; they join in small whole-number ratios. An atom is about in radius, and .
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) Atoms are neither created nor destroyed in a reaction, so the same atoms, with the same total mass, are there before and after.
Step 2. (b) Atoms of one element all have the same mass, and in a compound they join in a fixed ratio. So the masses of the elements are always in the same ratio.
Step 3. (c) Atoms join in small whole-number ratios: here .
Answer: (a) atoms are not created or destroyed; (b) a fixed ratio of atoms with fixed masses; (c) small whole-number ratios.
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