Download App

[ Question Bank ] - 2022 — Science STD 10 — Question

Maharashtra BoardEnglish MediumSTD 10Science[ Question Bank ] - 20225 Marks
Question
Explain Bayer’s process of concentration of bauxite with a chemical equation.
✓

Answer

1. Bauxite is the main ore of aluminium with silica $\left( SiO _2\right)$, ferric oxide $\left( Fe _2 O _3\right)$ and titanium oxide $\left( TiO _2\right)$ as impurities in it.
2. In this process, the bauxite ore is first crushed and then it is leached by heating with hot concentrated caustic soda $( NaOH )$ solution under high pressure for 2 to $8 hrs$ at 140 to $150^{\circ} C$ in a tank called a digester.
3. Aluminium oxide, being amphoteric in nature, dissolves in an aqueous $NaOH$ solution, forming water-soluble sodium aluminate.
$
\underset{\substack{\text { Aluminium } \\ \text { oxide }}}{ Al _2 O _3 \cdot 2 H _2 O _{( s )}}+\underset{\substack{\text { Sodium } \\ \text { hydroxide }}}{ NaOH _{( aq )}} \longrightarrow \underset{\substack{\text { Sodium } \\ \text { aluminate }}}{2 NaAlO _{2( aq )}}+\underset{\text { Water }}{3 H _2 O _{( l )}}
$
4. The iron oxide present in the gangue does not dissolve in an aqueous $NaOH$ solution and is separated by filtration.
5. However, silica from the gangue dissolves in an aqueous $NaOH$ solution forming water-soluble sodium silicate.
6. The solution of sodium aluminate is diluted with water and then cooled to $50^{\circ} C$. This gives aluminium hydroxide as a precipitate.
$
\underset{\substack{\text { Sodium } \\ \text { aluminate }}}{ NaAlO _{2( aq )}}+\underset{\text { Water }}{2 H _2 O _{( l )}} \longrightarrow \underset{\substack{\text { Sodium } \\ \text { hydroxide }}}{ NaOH _{( aq )}}+\underset{\substack{\text { Aluminium } \\ \text { hydroxide }}}{ Al ( OH )_3 \downarrow}
$
7. The aluminium hydroxide is then filtered, washed, dried and calcined by heating at $1000{ }^{\circ} C$ to get pure aluminium oxide, called alumina.
$\underset{\substack{\text { Aluminium } \\ \text { hydroxide }}}{2 Al ( OH )_{3( s )}} \stackrel{\text { heat }}{1000^{\circ} C } \underset{\substack{\text { Aluminium } \\ \text { oxide }}}{ Al _2 O _{3( s )}}+\underset{\text { Water vapour }}{3 H _2 O _{( g )}}$

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free

Explore more

More "Answer the following questions: [5 M]" from [ Question Bank ] - 2022→[ Question Bank ] - 2022 — all question types→Science STD 10 question papers→Maharashtra Board STD 10 question papers→Maharashtra Board question paper generator→

Similar questions

Draw a labelled diagram of the human male reproductive system. With the help of this diagram, describe the working of human male reproductive system?
→
A four carbons atoms containing neutral organic compound $X$ reacts with sodium metal to evolve a gas which burns with 'pop' sound. Another four carbon atoms containing carbon compound reacts with sodium hydrogen carbonate to evolve a gas which turns lime water milky. When compounds $X$ and $Y$ are heated together in the presence of a little of concentrated sulphuric acid, then a new compound $Z$ is formed.
  1. What is compound $X?$ Also write its formula.
  2. What is compound $Y?$ Also write its formula.
  3. What is compound $Z?$ Also write its formula.
  4. What type of smell is given by compound $Z?$
  5. What is the general name of compounds like $Z?$
  6. What is the general name of the reaction which which takes place between $X$ and $Y$ to form $Z?$
→
Write short note: Production of cheese.
→
Does pollution deplete the quality of air? Explain with suitable example.
→
An object placed 4cm in front of a converging lens produces a real image 12cm from the lens.
  1. What is the magnification of the image?
  2. What is the focal length of the lens?
  3. Draw a ray diagram to show the formation of image. Mark clearly F and 2F in the diagram.
→
Asexual reproductionSexual reproduction
1. Reproduction that occurs with the help of somatic cells is called asexual reproduction.1. ___________________________
2. ___________________________2. Male and female parent are necessary for sexual reproduction.
3. This reproduction occurs with the help of mitosis only.3. ___________________________
4. ___________________________4. New individual formed by this method is genetically different from parents.
5. Asexual reproduction occurs in different individuals by various methods like binary fission, multiple fission, budding, fragmentation, regeneration, vegetative propagation, spore production, etc.5. ___________________________
→
What is alcoholism? What are its effects?
→
What is electromagnetic induction? Who discovered it?
→
Explain the application of heating effect of electric current in an electric iron.
→
Give four uses of decomposition reaction.
→