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Ionic compounds contain ions - Edexcel - GCSE Chemistry Combined Science - Question 3 - 2016 - Paper 1
Question 3
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. | particle | electrons | ... show full transcript
Worked Solution & Example Answer:Ionic compounds contain ions - Edexcel - GCSE Chemistry Combined Science - Question 3 - 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 need to examine the relationship between the number of electrons and protons. A negative ion has more electrons than protons.
- Particle W: 9 electrons, 9 protons
- Not a negative ion (equal electrons and protons).
- Particle X: 10 electrons, 12 protons
- Not a negative ion (fewer electrons than protons).
- Particle Y: 16 electrons, 16 protons
- Not a negative ion (equal electrons and protons).
- Particle Z: 18 electrons, 16 protons
- This is a negative ion because it has 2 more electrons than protons.
Thus, particle Z is the negative ion.
Step 2
Calculate the relative formula mass of calcium nitrate, Ca(NO₃)₂.
Answer
First, we calculate the contributions from each element in the compound Ca(NO₃)₂:
-
Calcium (Ca):
- Relative atomic mass = 40
- There is 1 calcium atom:
-
Nitrogen (N):
- Relative atomic mass = 14
- There are 2 nitrogen atoms:
-
Oxygen (O):
- Relative atomic mass = 16
- There are 6 oxygen atoms (2 from each of the 3 nitrate ions):
Now, we sum all the contributions:
Therefore, the relative formula mass of calcium nitrate, Ca(NO₃)₂, is 164.