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Ionic compounds contain ions - Edexcel - GCSE Chemistry - Question 4 - 2016 - Paper 1
Question 4
Ionic compounds contain ions. (a) The numbers of electrons, neutrons and protons in four particles, W, X, Y and Z, are shown in Figure 5. Explain which particle, W... show full transcript
Worked Solution & Example Answer:Ionic compounds contain ions - Edexcel - GCSE Chemistry - Question 4 - 2016 - Paper 1
Step 1
Explain which particle, W, X, Y or Z, is a negative ion.
Answer
To determine which particle is a negative ion, we must examine the number of electrons and protons in each particle. A negative ion, or anion, is formed when an atom gains electrons, resulting in more electrons than protons.
- Particle W: 9 electrons, 9 protons.
- Particle X: 10 electrons, 12 protons.
- Particle Y: 16 electrons, 12 protons.
- Particle Z: 18 electrons, 16 protons.
From this information:
- W has equal numbers of electrons and protons, so it is neutral.
- X has more electrons (10) than protons (12), indicating a negative charge (negative ion).
- Y has more electrons (16) than protons (12), also indicating a negative charge (negative ion).
- Z has more electrons than protons (18 electrons vs. 16 protons), thus it is also a negative ion.
However, between X, Y, and Z, only X has a proton count that suggests it is less stable as a negative ion compared to Y and Z. Therefore, we conclude that the answer could include either Y or Z as a negative ion, but since multiple choices can be valid here, we can assert that:
- The particles X, Y, and Z are negative ions.
Step 2
Calculate the relative formula mass of calcium nitrate, Ca(NO₃)₂.
Answer
To calculate the relative formula mass of calcium nitrate, we start by determining the atomic masses of the elements involved:
- Calcium (Ca) = 40
- Nitrogen (N) = 14
- Oxygen (O) = 16
The formula for calcium nitrate is Ca(NO₃)₂. This indicates that there are:
- 1 Calcium atom
- 2 Nitrogen atoms
- 6 Oxygen atoms (since 3 × 2 = 6)
Now, we can calculate the total mass:
- Mass of Ca = 1 × 40 = 40
- Mass of N = 2 × 14 = 28
- Mass of O = 6 × 16 = 96
Adding these together gives:
Thus, the relative formula mass of calcium nitrate, Ca(NO₃)₂, is 164.