The much of the sample that would remain unchanged after 140 seconds is 2.813 g
Explanation
Half life is time taken for the quantity to reduce to half its original value.
if the half life for Scandium is 35 sec, then the number of half life in 140 seconds
=140 sec/ 35 s = 4 half life
Therefore 45 g after first half life = 45 x1/2 =22.5 g
22.5 g after second half life = 22.5 x 1/2 =11.25 g
11.25 g after third half life = 11.25 x 1/2 = 5.625 g
5.625 after fourth half life = 5.625 x 1/2 = 2.813
therefore 2.813 g of Scandium 47 remains unchanged.
First one is true second one is False
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The statement that best explains why magnesium and chlorine combine in a 1:2 ratio is; Magnesium has two valence electrons, and chlorine can accept one electron in its outer shell.
The number of electrons that an atom of an element has in its outermost shell determines the chemical formula of the compounds formed by atoms such elements.
Magnesium is in group 2, as such it has two electrons in its outermost shell while chlorine in group 17 only accepts one electron in its outermost shell. This one electron will give chlorine an inert gas configuration while the loss of two electrons give magnesium an inert gas configuration.
Therefore; The compound MgCl2 is formed in the ratio of 1:2 because Magnesium has two valence electrons, and chlorine can accept one electron in its outer shell.
Learn more: brainly.com/question/11527546
Since the molecule contains Hydrogen and is covalently bonded, it contains dipole-dipole forces and hydrogen bonds.
