<span>B) a cube with a ball stuck on each of its eight corners and one suspended at its center </span>
TMS stands for Tetramethylsilane
Formula : Si(CH₃)₄
It is used as internal standard for chemical shift
In TMS all the four methyl groups are similar thus all the 12 hydrogen are chemically equivalent. They will show proton NMR at same level and which will appear as a singlet.
We have defined this singlet to be as reference set as zero.
Generally the other organic compounds show chemical shift downfield.So have positive chemical shift with respect to TMS shift.
In one mole of talc, we observe that there are:
3 moles of Mg
4 moles of Si
2 moles of H
12 moles of O
The molar ratio of O to Mg is then:
12 moles of O : 3 moles of Mg = 4 : 1
Therefore, if 6.1 moles of Mg are present, the moles of O are:
4 * 6.1 = 24.4 moles of O