13.3 legislation of constant composition (ESADW)

In any given chemical compound, the elements constantly combine in the very same proportion with each other. This is the law of continuous composition.

The law of constant composition claims that, in any particular chemical compound, every samples of that compound will certainly be made up of the same aspects in the very same proportion or ratio. For example, any kind of water molecule is constantly made increase of two hydrogen atoms and also one oxygen atom in a \(2:1\) ratio. If we look at the loved one masses that oxygen and also hydrogen in a water molecule, we view that \(\text94\%\) of the mass of a water molecule is accounted because that by oxygen and also the staying \(\text6\%\) is the fixed of hydrogen. This massive proportion will be the exact same for any water molecule.

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This walk not median that hydrogen and oxygen always combine in a \(2:1\) ratio to kind \(\textH_2\textO\). Lot of proportions space possible. Because that example, hydrogen and also oxygen may combine in different proportions to type \(\textH_2\textO_2\) fairly than \(\textH_2\textO\). In \(\textH_2\textO_2\), the \(\textH:\textO\) proportion is \(1:1\) and also the mass ratio of hydrogen come oxygen is \(1:16\). This will be the exact same for any molecule of hydrogen peroxide.

Law of consistent composition


To inspection the ratio in i beg your pardon compounds combine.


\(\text0,1\) \(\textmol·dm$^-3$\) silver nitrate (\(\textAgNO_3\))

\(\text0,1\) \(\textmol·dm$^-3$\) sodium chloride (\(\textNaCl\))

\(\text0,1\) \(\textmol·dm$^-3$\) command nitrate (\(\textPbNO_3\))

\(\text0,1\) \(\textmol·dm$^-3$\) salt iodide (\(\textNaI\))

\(\text0,1\) \(\textmol·dm$^-3$\) stole (III) chloride (\(\textFeCl_3\))

\(\text0,1\) \(\textmol·dm$^-3$\) salt hydroxide (\(\textNaOH\))

9 large test tubes

3 propettes



Reaction 1: Prepare three test tubes with \(\text5\) \(\textmL\), \(\text10\) \(\textmL\) and \(\text15\) \(\textmL\) of silver- nitrate respectively. Using a clean propette include \(\text5\) \(\textmL\) of sodium chloride to every one and also observe what happens.

Reaction 2: Prepare three test tubes v \(\text5\) \(\textmL\), \(\text10\) \(\textmL\) and \(\text15\) \(\textmL\) of lead nitrate respectively. Making use of a clean propette add \(\text5\) \(\textmL\) of sodium iodide to every one and also observe what happens. Compose a balanced equation for this reaction.

Reaction 3: Prepare three test tubes v \(\text5\) \(\textmL\), \(\text10\) \(\textmL\) and \(\text15\) \(\textmL\) of salt hydroxide respectively. Include \(\text5\) \(\textmL\) the iron(III) chloride to every one and also observe what happens.

Discussion and also conclusion

Regardless the the quantity of reaction added, the same products, with the very same compositions, are developed (i.e. The precipitate it was observed in the reactions). However, if the reactants space not added in the correct ratios, there will be unreacted reactants the will continue to be in the last solution, along with the products formed.

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Volume relationships in gases (ESADX)

In a chemistry reaction in between gases, the loved one volumes that the gases in the reaction are current in a proportion of little whole numbers if every the gases space at the exact same temperature and also pressure. This partnership is also known as Gay-Lussac"s Law.

For example, in the reaction between hydrogen and oxygen to produce water, two volumes of \(\textH_2\) react v one volume the \(\textO_2\) to produce two volumes of \(\textH_2\textO\).

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\<2\textH_2\text(g) + \textO_2\text(g) \rightarrow 2\textH_2\textO (l)\>

In the reaction to develop ammonia, one volume that nitrogen gas reaction with three volumes that hydrogen gas to produce two volumes of ammonia gas.