Chemistry assignment

Thus we must multiply 3 to get the integers 3 and 4, for Fe and O subscripts respectively. This is the simplest, or empirical, formula because the subscripts are the smallest integers that express ratios of atoms present in the compound.
Certain elements appear to violate the rules in electron configuration. The electron configuration of chromium is rather than , as one might have expected. Similarly, the configuration of copper is instead of . This anomalous behavior is largely a consequence of the closeness of the 3d and 4s orbital energies. It frequently occurs when there are enough electrons to lead to precisely half-filled sets of degenerate orbitals (as in chromium) or to completely filled d subshell (as in copper).
Increasing the distance from the nucleus decreases the attraction between the electrons and the nucleus. As this attraction decreases, it becomes easier to remove the electron and, thus, lower ionization energy. Element A has the largest atomic number (greatest distance between outer electron and nucleus) because it has the least ionization energy.
The ionization energies for an element increase in magnitude as successive electrons are removed. But when the next electron removed is an inner-shell electron, there is a sharp increase in ionization energy. The figure shown below tells us which group elements A-E should be placed.
19. 27.823g of Na2CO3.xH2O crystals were dissolved in water and made up to 1000 cm3 of solution. 25 cm3 of this solution required 48.8 cm3 of 0.1 mol dm-3 HCI for complete neutralisation. Find the value of x in Na2CO3.xH2O using the following steps:
20. 4.00g of lawn sand (a mixture of sand and ammonium sulphate) was weighed into a conical flask, and 25 cm3 of 2.0 mol dm-3 sodium hydroxide solution was pipetted into the same flask. The conical flask was boiled for 20 minutes, after which time all the ammonia had been driven off,

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