In a workshop producing copper oxide glaze, a technician checks the particles present before firing a ceramic tile. The tile is heated to 1000 °C, although ...
Question 1 Report
In a workshop producing copper oxide glaze, a technician checks the particles present before firing a ceramic tile. The tile is heated to 1000 °C, although increasing temperature does not change the number of electrons in an ion. Fig. 1 compares an oxygen atom with an oxide ion. Each small dot represents one electron. During a reaction with a metal, an oxygen atom can gain electrons. This differs from sodium chloride, where sodium ions and chloride ions form a different ionic compound. The technician also measures the mass of copper oxide before and after heating in a sealed box so that no solid can escape.
Fig. 1
(a) Complete this statement: an oxygen atom gains ______ electrons to become an oxide ion. [1]
(b) Use Fig. 1 to write the electron arrangement of the oxygen atom and the oxide ion. [2]
(c) Explain why an oxide ion has a negative charge. [2]
(d) Describe how magnesium and oxygen form an ionic compound. [3]
(e) What happens to the total mass of copper oxide in the sealed box during heating and cooling? [2]
Answer Details
- (a) The oxygen atom gains two electrons to become an oxide ion. [1]
- (b) The oxygen atom has electron arrangement 2,6 [1]. The oxide ion has electron arrangement 2,8 [1].
- (c) The ion has gained electrons [1]. It has two more electrons than protons, so it has more negative than positive charge and is \(2-\) [1].
- (d) Magnesium loses two electrons [1], and oxygen gains these two electrons [1]. The resulting \(\text{Mg}^{2+}\) and \(\text{O}^{2-}\) ions attract because they have opposite charges, forming an ionic bond [1].
- (e) The total mass stays the same [1]. The box is sealed, so no material enters or leaves; particles are conserved during heating and cooling [1].
Exam reminder: Heating may change a substance’s temperature or state, but in a sealed system it does not change the total mass.
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