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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 assess the number of electrons, neutrons, and protons in each particle. A negative ion has 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 the data:
- Particle W has the same number of protons and electrons, indicating it is neutral.
- Particle X has more electrons (10) than protons (12), thereby indicating it is neutral too.
- Particle Y also has more electrons (16) than protons (12), indicating it is a negative ion.
- Particle Z has more electrons (18) compared to protons (16), indicating it is also a negative ion.
Since both Particle Y and Z have more electrons than protons, either could be considered a negative ion. However, typically it's noted that the one with the lesser number in other subatomic particles won't generally signify interest in ion charge discussion. Hence, the most straightforward answer is Particle Y is a negative ion.
Step 2
Calculate the relative formula mass of calcium nitrate, Ca(NO₃)₂.
Answer
To calculate the relative formula mass of calcium nitrate, Ca(NO₃)₂, we first identify the atomic masses of each element in the formula:
- Calcium (Ca): 40
- Nitrogen (N): 14
- Oxygen (O): 16
The formula Ca(NO₃)₂ indicates one calcium atom, two nitrogen atoms (from the 2 in front of NO₃), and six oxygen atoms (2 from the NO₃ parts and 3 from each part, totaling 6).
Now, calculate the total mass:
- Mass of Ca = 1 × 40 = 40
- Mass of N = 2 × 14 = 28
- Mass of O = 6 × 16 = 96
Therefore, the total relative formula mass is:
Thus, the relative formula mass of calcium nitrate, Ca(NO₃)₂, is 164.