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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 need to look for a particle with more electrons than protons. This is because negative ions are formed when atoms gain electrons.
Examining the particles:
- W: Electrons = 9, Protons = 9 (neutral)
- X: Electrons = 10, Protons = 12 (neutral)
- Y: Electrons = 16, Protons = 12 (negative ion)
- Z: Electrons = 18, Protons = 16 (negative ion)
From this observation, both particles Y and Z have more electrons than protons, making them negative ions. Therefore, W is neither negative nor positive, and X is also neutral. The correct answers for a negative ion are particles Y or Z.
Step 2
Calculate the relative formula mass of calcium nitrate, Ca(NO₃)₂.
Answer
To calculate the relative formula mass of calcium nitrate, we first need to find the masses of each element in the formula.
The formula for calcium nitrate is Ca(NO₃)₂, which consists of:
- 1 Calcium (Ca) atom
- 2 Nitrogen (N) atoms
- 6 Oxygen (O) atoms (because there are 3 oxygen atoms for each nitrate, multiplied by 2 nitrates)
Now, using the relative atomic masses provided:
- Ca = 40
- N = 14
- O = 16
Now we calculate the total:
total mass = (1 × 40) + (2 × 14) + (6 × 16)
total mass = 40 + 28 + 96 = 164
Thus, the relative formula mass of calcium nitrate, Ca(NO₃)₂, is 164.