Chemistry

Mole Concept and Stoichiometry

354 Questions

The mole concept is a core area of chemistry focusing on the quantitative relationships between reactants and products in chemical reactions. Questions cover molecular mass calculations, stoichiometric conversions, and determining the number of molecules. This topic is essential for most science entrance and competitive examinations.

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Mole Concept and Stoichiometry Questions

Multiple choice

Pure gold is

  1. 22 carat

  2. 100 carat

  3. One carat

  4. 24 carat
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Ans : 4.

Multiple choice

Waxy solids alkanes contains

  1. 22 and 27 carbon atoms

  2. Upto 4 carbon atoms

  3. 5 to 19 carbons

  4. Closed loop of Carbon and Hydrogen atoms
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Alkanes, which are the major constituents of crude oil, do not mix with water and float on its surface. The wax that we call paraffin and make candles from is a mixture of alkanes containing between 22 and 27 carbon atoms per molecule.

Multiple choice

What is the molecular mass of water?

  1. 34

  2. 33

  3. 20

  4. 18
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The chemical formula for water is H2O. The atomic mass of hydrogen is approximately 1 and oxygen is 16, so the molecular mass is (2 * 1) + 16 = 18.

Multiple choice

The empirical formula of diamond is?

  1. D

  2. C

  3. Di

  4. All of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Diamond is a pure form of carbon. Its empirical formula is simply the symbol for carbon, which is C.

Multiple choice

Which of the following statements is false about a compound, which is combined in the fixed proportion?

  1. 4 grams of hydrogen combine with 32 grams of oxygen to give 36 grams of water.

  2. In the molecule of carbon dioxide, carbon and oxygen are present in fixed ratio of 3 : 8 by mass.

  3. In the molecule of water, hydrogen and oxygen are present in the ratio of 1 : 8.

  4. 12 grams of carbon combine with 32 grams of oxygen to give 40 grams of carbon dioxide.

  5. In the molecule of carbon monoxide (CO), the ratio of carbon and oxygen is 3 : 8.
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

In the molecule of carbon monoxide (CO), the ratio of carbon and oxygen is 3 : 4, but not 3 : 8[CARBON : OXYGEN = 12 : 16 = 3 : 4]

Multiple choice

If M is molecular wt of the ion IO4-, what is the equivalent mass if it is converted into I2 in acidic medium?

  1. <span style="font-size:11.0pt;line-height:115%;font-family:"Calibri","sans-serif";mso-ascii-theme-font:minor-latin;mso-fareast-font-family:Calibri;mso-fareast-theme-font:minor-latin;mso-hansi-theme-font:minor-latin;mso-bidi-theme-font:minor-latin;mso-ansi-language:EN-US;mso-fareast-language:EN-US;mso-bidi-language:AR-SA">M/6

  2. <span style="font-size:11.0pt;line-height:115%;font-family:"Calibri","sans-serif";mso-ascii-theme-font:minor-latin;mso-fareast-font-family:Calibri;mso-fareast-theme-font:minor-latin;mso-hansi-theme-font:minor-latin;mso-bidi-theme-font:minor-latin;mso-ansi-language:EN-US;mso-fareast-language:EN-US;mso-bidi-language:AR-SA">M/7

  3. <span style="font-size:11.0pt;line-height:115%;font-family:"Calibri","sans-serif";mso-ascii-theme-font:minor-latin;mso-fareast-font-family:Calibri;mso-fareast-theme-font:minor-latin;mso-hansi-theme-font:minor-latin;mso-bidi-theme-font:minor-latin;mso-ansi-language:EN-US;mso-fareast-language:EN-US;mso-bidi-language:AR-SA">M/5

  4. <span style="font-size:11.0pt;line-height:115%;font-family:"Calibri","sans-serif";mso-ascii-theme-font:minor-latin;mso-fareast-font-family:Calibri;mso-fareast-theme-font:minor-latin;mso-hansi-theme-font:minor-latin;mso-bidi-theme-font:minor-latin;mso-ansi-language:EN-US;mso-fareast-language:EN-US;mso-bidi-language:AR-SA">M
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

For conversion of IO4- to I2 in acidic medium the reaction is as under. IO4- + 7e- → I2……………… here oxidation state of I in IO4- is +7 and in I2 is 0, so gain in number of electrons is of +7. We know that equilibrium weight is given by eqilibrium weight = molecular mass/gain in number of electrons = M/7

Multiple choice

A formula representing the simplest ratio of atoms in a molecule is

  1. chemical formula

  2. molecular formula

  3. empirical formula

  4. structural formula

Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

An empirical formula represents the simplest whole number ratio of various atoms present in a compound. If the mass per cent of various elements present in a compound is known, it's empirical formula can be determined. Molecular formula can further be obtained if the molar mass is known.