Question
The table gives some properties of an element.
Which other property does this element have?
A. acts as a catalyst
B. brittle
C. forms an acidic oxide
D. highly reactive with water
▶️Answer/Explanation
Ans:
A
Molybdenum itself is a silvery-grey metal, similar in appearance to other transition metals.
Molybdenum chloride exists in different oxidation states, resulting in different chloride compounds. One example is Molybdenum(IV) chloride (MoCl4), which is a dark blue compound.
Molybdenum compounds, including molybdenum chloride, can act as catalysts in various chemical reactions. They are particularly useful in catalyzing reactions involving carbon-carbon bond formation, such as olefin metathesis and hydrodesulfurization. The high melting point you mentioned, 3422°C, is a characteristic property of molybdenum itself, rather than its chloride compounds.
Question
The properties of the element titanium, Ti, can be predicted from its position in the Periodic Table. Which row identifies the properties of titanium?
▶️Answer/Explanation
Ans:B
Titanium can be used as a catalyst in various chemical reactions. Titanium-based catalysts find applications in several industrial processes and organic transformations.
Being a transition metal, titanium tends to have a relatively high density and melting point.
Titanium is a transition metal, which generally exhibits metallic properties such as high thermal and electrical conductivity, malleability, and ductility.
Titanium, a transition metal is known for forming colored compounds. The presence of different oxidation states and coordination environments in titanium compounds contributes to their vibrant colors.
Question
An element melts at \(1455^o\)C, has a density of 8.90 g / \(cm^3\) and forms a green chloride.
Where in the Periodic Table is this element found?
▶️Answer/Explanation
Ans: C
Its high melting point, high density and colored chloride properties indicate that it is a transition element. It is C.
Question
When aqueous sodium hydroxide is added to a solution of a metal ion, a grey-green precipitate forms, which dissolves in excess to form a dark green solution.
What is the identity of the metal ion?
A chromium(III)
B iron(II)
C iron(III)
D copper(II)
▶️Answer/Explanation
Ans: A
When sodium hydroxide is added to the solution containing chromium(III) ions, a grey-green precipitate forms. This precipitate is likely chromium(III) hydroxide. If more sodium hydroxide is added to the grey-green precipitate, it will dissolve, forming a dark green solution. This dissolution occurs because the excess hydroxide ions react with the chromium(III) hydroxide to form a complex ion. The dark green color of the resulting solution is due to the formation of the hexahydroxochromate(III) complex ion.
Question
Copper is a transition element.
Two compounds of copper are copper(II) oxide and copper(II) carbonate.
Which row describes the two compounds?
▶️Answer/Explanation
Ans: C
Metal oxides are basic. Copper(II) oxide is also basic.
Copper(II) carbonate is commonly known for its green color. The green color arises due to the presence of the copper(II) ion in the compound.