1.How would you separate a mixture of salt, sawdust, and iron filings?
2. The Mg^2+ and Na^+ ions have ten electrons. Which has the smaller radius? Explain.
From my high school chemistry class almost 60 years ago --
Use a magnet to pull out the iron filings. Water will dissolve the salt. The sawdust will remain.
Ms. Sue remembers her chemistry from 60 years ago. Yea!
For #2,consider the charge on the Na nucleus versus the charge on the Mg nucleus.
1. To separate a mixture of salt, sawdust, and iron filings, you can use the following steps:
a) Use a magnet to remove the iron filings: Iron filings are magnetic, so by passing a magnet over the mixture, the iron filings will be attracted to the magnet and can be separated easily.
b) Dissolve the mixture in water: Salt is water-soluble, while sawdust is insoluble. By adding water to the remaining sawdust and salt mixture, the salt will dissolve, leaving the sawdust behind.
c) Filtration: Use a filter paper or a fine mesh sieve to separate the sawdust from the water-salt solution. The sawdust will be trapped by the filter, while the water-salt solution will pass through.
d) Evaporation: To separate the salt from the water, you can simply heat the solution, allowing the water to evaporate. The salt will remain behind as a solid residue.
2. The radius of an ion is dependent on the number of protons, electrons, and the overall charge of the ion. In this case, both Mg2+ and Na+ ions have a charge of +2 as they lose two electrons to achieve a stable octet configuration.
Now, let's compare the two ions:
Mg2+ ion: In its ground state, a magnesium atom has 12 electrons. When it loses two electrons, it becomes Mg2+ with a valence shell of 10 electrons. With 10 electrons, the effective nuclear charge from the 12 protons in the nucleus is relatively higher, causing the valence electrons to be pulled closer to the nucleus. This results in a smaller radius for the Mg2+ ion compared to the neutral magnesium atom.
Na+ ion: In its ground state, a sodium atom has 11 electrons. When it loses one electron, it becomes Na+ with a valence shell of 10 electrons. With one less electron, the effective nuclear charge from the 11 protons becomes slightly higher. However, since Na+ has one less positive charge compared to Mg2+, the attractive force between the valence electrons and the nucleus is slightly weaker. As a result, the Na+ ion has a larger radius compared to the neutral sodium atom.
Therefore, the Na+ ion has a larger radius than the Mg2+ ion.