The Language of Chemistry Quiz - ICSE Class 9 Chemistry

Free practice quiz: The Language of Chemistry (ICSE Class 9 Chemistry). 52 multiple-choice questions with answers and explanations. Play online, no sign-up needed.

Sample questions

1. Which of the following is an example of a chemical symbol that represents an element discovered in the 20th century?

   1. Au
   2. Fe
   3. Tc
   4. Cu
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   Answer: C. Tc

   Au represents Gold, discovered long before the 20th century. Fe represents Iron, also known since antiquity. Cu represents Copper, another element known since antiquity. Tc represents Technetium, which was first synthesized in the 20th century.

2. In the chemical formula for iron(III) chloride, what does the Roman numeral 'III' indicate?

   1. The number of chlorine atoms
   2. The charge of the iron ion
   3. The mass number of iron
   4. The atomic number of iron
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   Answer: B. The charge of the iron ion

   Roman numerals in the names of ionic compounds indicate the oxidation state (charge) of the metal cation when the metal can form ions with multiple charges. Iron(III) chloride indicates iron with a +3 charge (Fe^3+).

3. The chemical formula for sulfuric acid is H2SO4. The '2' following H indicates:

   1. The total number of atoms in the molecule
   2. The valence of sulfur
   3. The number of hydrogen atoms
   4. The molecular weight of hydrogen
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   Answer: C. The number of hydrogen atoms

   In a chemical formula, subscripts indicate the number of atoms of the preceding element. Therefore, the subscript '2' in H2SO4 signifies two hydrogen atoms.

4. If an atom has an atomic number of 17 and a mass number of 35, how many neutrons does it have?

   1. 17
   2. 18
   3. 35
   4. 52
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   Answer: B. 18

   The atomic number is equal to the number of protons. The mass number is the sum of protons and neutrons. Number of neutrons = Mass Number - Atomic Number = 35 - 17 = 18.

5. The chemical formula for carbon dioxide is CO2. What does the subscript '2' indicate?

   1. The number of carbon atoms
   2. The number of oxygen atoms
   3. The total number of atoms
   4. The molecular weight of carbon
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   Answer: B. The number of oxygen atoms

   The subscript '2' in CO2 indicates that there are two atoms of oxygen.

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