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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 identify which particle is a negative ion, we must look for the particle that has more electrons than protons.
- W: 9 electrons, 9 protons (neutral)
- X: 10 electrons, 12 protons (positive ion)
- Y: 16 electrons, 12 protons (negative ion)
- Z: 18 electrons, 16 protons (negative ion)
From this, both Y and Z have more electrons than protons; however, Y has a lower electron count and is more likely to be a common ion, whereas Z, with a higher charge difference, is more definitively the negative ion. Therefore, Z is the negative ion.
Step 2
Calculate the relative formula mass of calcium nitrate, Ca(NO₃)₂.
Answer
The formula for calcium nitrate is Ca(NO₃)₂. To calculate the relative formula mass:
- Calculate for Calcium (Ca): 1 × 40 = 40
- Calculate for Nitrogen (N): 2 × 14 = 28
- Calculate for Oxygen (O): 6 × 16 = 96
Now sum these values:
Thus, the relative formula mass of calcium nitrate is 164.