13.3 legislation of consistent composition (ESADW)

In any type of given chemistry compound, the elements always combine in the exact same proportion v each other. This is the law of constant composition.

The law of continuous composition states that, in any details chemical compound, all samples of the compound will be made up of the same aspects in the exact same proportion or ratio. Because that example, any type of water molecule is constantly made increase of 2 hydrogen atoms and also one oxygen atom in a \(2:1\) ratio. If we look at the family member masses the oxygen and hydrogen in a water molecule, we see that \(\text94\%\) of the fixed of a water molecule is accounted for by oxygen and the staying \(\text6\%\) is the massive of hydrogen. This fixed proportion will be the same for any water molecule.

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This does not typical that hydrogen and also oxygen constantly combine in a \(2:1\) proportion to kind \(\textH_2\textO\). Lot of proportions are possible. Because that example, hydrogen and also oxygen may combine in various proportions to kind \(\textH_2\textO_2\) quite than \(\textH_2\textO\). In \(\textH_2\textO_2\), the \(\textH:\textO\) ratio is \(1:1\) and also the mass proportion of hydrogen come oxygen is \(1:16\). This will be the same for any molecule the hydrogen peroxide.

Law of continuous composition


To investigate the ratio in i m sorry 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 (\(\textNaI\))

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

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

9 large test tubes

3 propettes



Reaction 1: Prepare 3 test tubes v \(\text5\) \(\textmL\), \(\text10\) \(\textmL\) and \(\text15\) \(\textmL\) of silver nitrate respectively. Utilizing a clean propette include \(\text5\) \(\textmL\) of sodium chloride to each one and also observe what happens.

Reaction 2: Prepare 3 test tubes through \(\text5\) \(\textmL\), \(\text10\) \(\textmL\) and also \(\text15\) \(\textmL\) of lead nitrate respectively. Making use of a clean propette include \(\text5\) \(\textmL\) of sodium iodide to each one and also observe what happens. Write a well balanced equation because that this reaction.

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

Discussion and also conclusion

Regardless of the lot of reaction added, the exact same products, through the same compositions, are formed (i.e. The precipitate it was observed in the reactions). However, if the reactants are not added in the exactly ratios, there will certainly be unreacted reactants the will stay in the final solution, along with the commodities formed.

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Volume relationships in gases (ESADX)

In a chemistry reaction in between gases, the family member volumes the the gases in the reaction are existing in a ratio of little whole numbers if every the gases space at the exact same temperature and also pressure. This connection is also known together Gay-Lussac"s Law.

For example, in the reaction between hydrogen and also oxygen to develop water, two volumes that \(\textH_2\) react through 1 volume of \(\textO_2\) to create 2 quantities 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 produce ammonia, one volume of nitrogen gas reaction with three volumes of hydrogen gas to produce two volumes of ammonia gas.