Inorganic Chemistry

Question 1

Which of the following is the oxidation state of chromium in potassium dichromate (K2Cr2O7)?

Accepted Answer

+6

Answer

In potassium dichromate (K2Cr2O7), potassium (K) has an oxidation state of +1, and oxygen (O) typically has an oxidation state of -2. To find the oxidation state of chromium (Cr), we set up the equation: 2(+1) + 2(Cr) + 7(-2) = 0. Solving this gives 2 + 2Cr - 14 = 0, which simplifies to 2Cr = 12, so Cr = +6.

Question 2

What is the geometry of the ammonia (NH3) molecule according to the VSEPR theory?

Accepted Answer

Trigonal pyramidal

Answer

According to VSEPR theory, the geometry of a molecule is determined by the repulsion between electron domains around the central atom. In ammonia (NH3), the central nitrogen atom has three bonding pairs with hydrogen atoms and one lone pair of electrons. These four electron domains arrange themselves in a tetrahedral electron geometry, but the lone pair exerts greater repulsion, distorting the molecular geometry into a trigonal pyramidal shape.

Question 3

Which compound is known as quicklime?

Accepted Answer

Calcium oxide

Answer

Quicklime is the common name for calcium oxide (CaO). It is a white, caustic, alkaline crystalline solid at room temperature. Calcium oxide is produced by the thermal decomposition of materials like limestone (calcium carbonate, CaCO3) in a process called calcination, and it is widely used in various industrial applications.

Question 4

Which of the following elements is a transition metal?

Accepted Answer

Iron

Answer

Transition metals are elements that have partially filled d-orbitals in their atoms or form ions with partially filled d-orbitals. They are located in groups 3-12 of the periodic table. Iron (Fe) is found in Group 8 and Period 4, possessing characteristic properties of transition metals such as variable oxidation states and the formation of colored compounds.

Question 5

What type of bond exists in sodium chloride (NaCl)?

Accepted Answer

Ionic bond

Answer

An ionic bond forms between a metal and a non-metal due to the complete transfer of electrons, creating oppositely charged ions that are electrostatically attracted. In sodium chloride (NaCl), sodium (a metal) donates an electron to chlorine (a non-metal), forming a positively charged sodium ion (Na+) and a negatively charged chloride ion (Cl-). The strong electrostatic attraction between these ions constitutes the ionic bond.

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Inorganic Chemistry