Answer:
Option D. fluorine-18
Explanation:
The attached photo gives the explanation.
In the attached photo, A zX represent the atom that will undergo beta decay to produce oxygen–18.
After the calculation, A zX was found to be fluorine–18.
The moles of potassium dichromate , K₂Cr₂O₇ are required to prepare a 250 mL solution of with a concentration of 2.16 M is 0.54 mol.
given that :
molarity = 2.16 M
volume = 250 mL = 0.25 L
the molarity is given as :
molarity = number of moles / volumes in L
from this we can calculate the number of moles, we get :
number of moles of K₂Cr₂O₇ = molarity × volume
number of moles of K₂Cr₂O₇ = 2.16 × 0.25
number of moles of K₂Cr₂O₇ = 0.54 mol
Thus, The moles of potassium dichromate , K₂Cr₂O₇ are required to prepare a 250 mL solution of with a concentration of 2.16 M is 0.54 mol.
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D - density: 13,534 g/ml
m - mass: 10g
V - volume: ??
_____________
d = m/V
V = m/d
V = 10/13,534
V = 0,7389 ml
:•)
As iron heats up, the arrangement of its atoms changes several times before it melts. ... Iron is magnetic at room temperature, and previous work predicted that iron's magnetism favors its open structure at low temperatures, but at 770 degrees Celsius iron loses its magnetism.
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