Tag: chemistry

Questions Related to chemistry

Artificial rubies and sapphires can be made by heating alumina in ?

chemistry combustion structure of flame flame combustion, fuels and flame

  1. An oxy-hydrogen flame

  2. An oxy-acetylene flame

  3. Burning methane

  4. An electric furnace

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Correct Option: A
Explanation:

Artificial ruby and sapphires are manufactured from alumina to which 1.5% of magnetic iron oxide and 0.5% of titanium oxide has been added, the mixture is fused and crystallised in an oxy-hydrogen flame. It is a reducing flame.

A lilac-coloured flame is produced on heating.

chemistry combustion structure of flame flame combustion, fuels and flame

  1. Potassium in a flame

  2. Cobalt in a flame

  3. Sodium in a flame

  4. Methane in oxygen

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Correct Option: A
Explanation:
Potassium on heating produced lilac-colured flame because on heating, an atom entities its electrons and they jump to higher energy levels. When the electron return to lower energy levels, they emit energy in the form of light. The colour produced on heating depends upon wavelength of emitted light.

If you watch a burning candle carefully, you will find different colurs in the flame. Which is the hottest part of the candle flame?

chemistry combustion structure of flame flame combustion, fuels and flame

  1. The middle orange part

  2. The middle, yellow part

  3. The outermost portion that is blue

  4. The innermost black zone

Show answer
Correct Option: C
Explanation:

The outermost portion that is blue.

The hottest part of the candle flame is the blue part, at $1670^oF$ ($1400^oC$) i.e., the outermost portion, where the flame has the most oxygen and you are getting complete combustion.

The flame of the candle has three zones. The outer zone is blue, the middle zone is yellow and the inner zone is black. Which is correct regarding this?

chemistry combustion structure of flame flame combustion, fuels and flame

  1. The outer zone is hottest hot.

  2. The middle zone is hottest

  3. The inner zone is least hot

  4. All the zones have same temperature

Show answer
Correct Option: A,C
Explanation:

Candles produce light by releasing heat. A candle flame consists of three zones. Each zone has different temperatures and colors.

  • The first zone is called the Outer zone
  • The second zone is called the Middle zone
  • The third zone is called the Inner zone

The outer zone is blue in color, due to complete combustion,. This zone is the hottest zone.

The middle one is in yellow color, which is the bright part of the flame. It is moderately hot and partial combustion of fuel takes place.

The least hot region of the flame is innermost zone. This inner zone is black in color due to the presence of unburnt wax vapors.

Pick one material which is completely soluble in water:

chemistry nature of things objects that float or sink substances that sink or float soluble and insoluble substances

  1. oil

  2. sawdust

  3. mud

  4. alum

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Correct Option: D
Explanation:

Alum is a hydrated double salt sometimes used as water purifier is completely soluble in water.

Select a pair of solute and solvent materials to form solution:

chemistry nature of things objects that float or sink substances that sink or float soluble and insoluble substances

  1. Chalk powder and water

  2. Alcohol and water

  3. Milk and oil

  4. Glass and water

Show answer
Correct Option: B
Explanation:

In general, organic compounds are insoluble in water. Though alcohol is an organic compound it is soluble in water due to hydrogen bonding. 

Find odd one out on the basis of the solubility of the material.

chemistry nature of things objects that float or sink substances that sink or float soluble and insoluble substances

  1. Sugar

  2. Salt

  3. Chalk

  4. Wood

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Correct Option: D
Explanation:

Wood is not at all soluble in water whereas sugar and salt are soluble and chalk $(CaCO _3)$ is slightly soluble in water.

Which of the following floats on water?

chemistry nature of things objects that float or sink substances that sink or float soluble and insoluble substances

  1. Air filled tube of a tyre

  2. A sharpener

  3. A stone

  4. A chain

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Correct Option: A
Explanation:

Air filled tube floats on water as it contain air and which is very less dense than water.

The EMF of the cell: Ag, AgCl in $0.1 M - KCl \parallel$ satd. $ NH _{4}NO _{3}\parallel 0.1 M - Ag NO _{3},$ Ag is 0.42 V at $ 25^{\circ}C.$ 0.1 M-KCl is 50% dissociated and $0.1 M - Ag NO _{3}$ is 40% dissociated. The solubility product of $ AgCl $ is $ (2.303 RT/F = 0.0)$

chemistry nature of things objects that float or sink substances that sink or float soluble and insoluble substances

  1. $1.0 \times 10^{-10} $

  2. $ 2.0 \times 10^{-9} $

  3. $ 1.0 \times 10^{-9}$

  4. $ 2.0 \times 10^{-10} $

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Correct Option: D

Maximum of 9.72 g of potassium chloride dissolves in 30 g of water at $70^{\circ}$C. The solubility of potassium chloride at $70^{\circ} C$ is:

chemistry nature of things objects that float or sink substances that sink or float soluble and insoluble substances

  1. 3.24 g

  2. 32.4 g

  3. 0.324 g

  4. 33.4 g

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Correct Option: B
Explanation:

Solubility is defined as solubility of different substances in grams per 100 gm of water.
30 gm of water dissolves 9.72 g of $KCl$.
So, 100gm will dissolve in $9.72\times 100/30=32.4$ gm.