Tag: general properties of transition metals

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Multiple choice chemistry d- and f-block elements some important compounds of transition elements general properties of transition metals the d-and f-block elements
Mass (g)
Empty crucible $22.01$
Crucible and copper oxide $42.01$
Crucible and copper product $(1^{st}mass)$ $39.87$
Crucible and copper product $(2^{nd}mass)$ $38.01$
Crucible and copper product $(3^{rd}mass)$ $38.01$

Copper ions can have multiple oxidative states. The data table above was obtained during a lab in which an unknown copper oxide was heated in a crucible.
From this data, what is the name of the unknown copper oxide?

  1. Copper(I) oxide.

  2. Copper (II) oxide.

  3. Copper (I) peroxide.

  4. Copper (II) peroxide.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Subtract the mass of the empty crucible (22.01 g) from the final copper product mass (38.01 g) to find the mass of copper, which is 16.00 g. Subtract the copper mass from the mass of the crucible and copper oxide (42.01 g - 22.01 g = 20.01 g total oxide minus copper gives oxygen mass), yielding 4.00 g of oxygen. Calculating the mole ratio of copper to oxygen gives 16.00/63.55 = 0.25 moles of Cu and 4.00/16.00 = 0.25 moles of O, resulting in a 1:1 empirical formula of CuO, which is copper(II) oxide.

Multiple choice chemistry d- and f-block elements some important compounds of transition elements general properties of transition metals the d-and f-block elements
State True or False.
Fe$ _3$O$ _4$ is mixed oxide of FeO and Fe$ _2$O$ _3$. 

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Iron (II,III) oxide is the chemical compound with formula $Fe _3O _4$. It occurs in nature as the mineral magnetite. It is one of a number of iron oxides, the others being iron(II) oxide ($FeO$), which is rare, and iron(III) oxide ($Fe _2O _3$) also known as hematite. $Fe _3O _4$ contains both $Fe^{2+}$ and $Fe^{3+}$ ions and is sometimes formulated as FeO ∙ Fe2O3.