Equation for Half life :
A = a(0.5)^(t/h)
A is current amount, "a" is initial amount, h is halflife, t is time
5 = 40(0.5)^(t/1.3x10^9)
5/40 = (0.5)^(t/1.3x10^9)
take the log of both sides , power rule
Log(5/40) = (t/1.3x10^9) * Log(0.5)
(1.3x10^9) * Log(5/40) / Log(0.5) = t
3.9x10^9 years = t
And if you think about what a half life is, the time it take for the amount to reduce to half.
40/2 = 20
20/2 = 10
10/2 = 5
It went through 3 half-lifes
3 * 1.3x10^9 = 3.9x10^9 years
Answer: 400K
Explanation:
Given that,
Original volume of balloon V1 = 3.0L
Original temperature of balloonT1 = 27°C
Convert the temperature in Celsius to Kelvin
(27°C + 273 = 300K)
New volume of balloon V2 = 4.0L
New temperature of balloon T2 = ?
Since volume and temperature are given while pressure is constant, apply the formula for Charle's law
V1/T1 = V2/T2
3.0L/300K = 4.0L/T2
To get the value of T2, cross multiply
3.0L x T2 = 4.0L x 300K
3.0LT2 = 1200LK
Divide both sides by 3.0L
3.0LT2/3.0L = 1200LK/3.0L
T2 = 400K
Thus, at a temperature of 400 Kelvin, the balloon would have a volume of 4.0L.
The correct option is D.
When dissolving a substance in a solvent, stirring the solution will increased the rate at which the substance dissolved. This is because, when one stirs a solution, it exposes more surface area of the solute to the solvent, thus, increasing the interaction between the solute and the solvent. The higher the quantity of the solute that is exposed to the solvent, the higher the rate of dissolution of the solute.
Answer:
The number of atoms in 20 grams of Pa-234 is 5.14 ×10²² atoms
Explanation:
Given that the molar mass of Pa-234 (protactinium) is 234.04331, we have
The number of moles of protactinium in 20 grams of Pa-234, we have
Number of moles = Mass/(Molar mass) = 20/234.04331 = 0.0855 moles
One mole of Pa-234 contains 6.02×10²³ atoms, therefore, we have;
0.0855 moles of Pa-234 contains 0.0855× 6.02×10²³ = 5.14 ×10²² atoms
Therefore, the number of atoms in 20 grams of Pa-234 = 5.14 ×10²² atoms.
