Question
Explain the term $: Mole$
✓
Answer
The $mole$ is a unit of measurement for the amount of substance. Moles give us a consistent method to convert between atoms/molecules and grams.
The mathematical expression for calculating moles is expressed as:
$moles =$ mass / molar mass
We can express moles in terms of molecular mass, number of atoms/molecules and in terms of volume.
The mathematical expression for calculating moles is expressed as:
$moles =$ mass / molar mass
We can express moles in terms of molecular mass, number of atoms/molecules and in terms of volume.
- $1\ mole$ of a pure substance has a mass in grams equal to its molecular mass.
- $1 \ mole$ contains the same number of particles as there are in $12g$ of carbon-$12$ atoms. This number is called Avogadro’s number and is equal to $6.023 \times 10^{23}$ particles.$1 \ mole$ of a gas occupies a volume of: $22.4$ litres at $\text{S.T.P}.$
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→(a) Which solution is used to react with bauxite as first step in obtaining pure aluminium oxide?
(b) The aluminium oxide for the electrolytic extraction of aluminium is obtained by heating aluminium hydroxide. Write the equation for this reaction.
(c) Name the element which serves both as the anode and the cathode in the extraction of aluminium.
(d) Write the equation for the reaction that occurs at the cathode during the extraction of aluminium.
(e) Write the equation for the reaction that occurs at the cathode during extraction of aluminium by electrolysis.
(f) Give the equation for the reaction that occurs at the anode when aluminium is purified by electrolysis.
Explain hydronium ion. Write the ionization of sulphuric acid showing the formation of hydronium ion.
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(i) Write the formula of cryolite.
(ii) Write down the word which correctly completes the following sentence.
"By dissolving aluminium oxide in cryolite, a ______ (conducting / non- conducting) solution is produced.
(iii) Why so much graphite required for this electrolytic process.
(iv) Write the equation for the reaction which takes place at cathode.
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| Insoluble base + .......... | Salt (soluble) + water | ……………. |
| Active metal + Acid (dil) | ………… + ………… | ……………. |
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| Chlorides/nitrates + Acid (conc) | …………. + ………… | Decomposition of chlorides and nitrates |
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(i) Predict the pH value of the water of river Yamuna if the reason for froth is high content of detergents dissolved in it.
(ii) The pH value of four solutions P, Q, R and S are 2, 9, 5 and 11 respectively. Arrange the solutions in in- creasing order of their hydronium ion concentration. Identify strong acid.
(iii) When the water has detergents dissolved in it. What is the level of concentration of hydronium ion and hydroxide ion?
(iv) If a sample of water containing detergents is provided to you, which method will you adopt to neutralise it?
