V=84.0 mL = 84.0 cm³
m=609.0 g
p=m/v
p=609.0/84.0=7.25 g/cm³
2.05 × 10²³ formula units
Given data:Mass of AgF = 43.15 gNumber of formula units = ?Solution:Number of moles of AgF:Number of moles = mass/ molar massNumber of moles = 43.15 g/ 126.87 g/molNumber of moles = 0.34 molNow Number of formula units will be determine by using Avogadro number.It is the number of atoms , ions and molecules in one gram atom of element, one gram molecules of compound and one gram ions of a substance.The number 6.022 × 10²³ is called Avogadro number1 mole = 6.022 × 10²³ formula units0.34 mol × 6.022 × 10²³ formula units2.05 × 10²³ formula units
Because 25% is half of 0.5 and the half life of is given as 5,715, the time it takes to reach this amount should just be double the half life: 11430 years.
However, in other cases the problem may not have easy numbers, so below is a more mathematical approach.
The half life formula is .
Solving for t gives:
Given information:
Plug in given values and solve for t.
With correct significant figures, this would be 11000 years.
Microscope, magnifying glass,
C. a snake hides under a rock on a hat day