Answer: a) %(C/Co) = (e^(-0.027t)) × 100
b) t1/2 = 25.67years
c) 5.872%
Explanation:
a) Radioactive reactions always follow a first order reaction dynamic
Let the initial concentration of Strontium-90 be Co and the concentration at any time be C
The rate of decay will be given as:
(dC/dt) = -KC (Minus sign because it's a rate of reduction)
The question provides K = 2.7% per year = 0.027/year
(dC/dt) = -0.027C
(dC/C) = -0.027dt
∫ (dC/C) = -0.027 ∫ dt
Solving the two sides as definite integrals by integrating the left hand side from Co to C and the Right hand side from 0 to t.
We obtain
In (C/Co) = -0.027t
(C/Co) = (e^(-0.027t))
In percentage, %(C/Co) = (e^(-0.027t)) × 100
(Solved)
b) Half life of a first order reaction (t1/2) = (In 2)/K
K = 0.027/year
t1/2 = (In 2)/0.027 = 25.67 years
c) percentage that remains after 105years,
%(C/Co) = (e^(-0.027t)) × 100
t = 105
%(C/Co) = (e^(-0.027 × 105)) × 100 = 5.87%
<h3><u>Answer;</u></h3>
2.4 atm
<h3><u>Explanation;</u></h3>
At constant temperature;
PV = constant
P1 = 1.2 atm
V1 = 0.25 L
P2 = ?
V2 = 0.125 L
But;
P1*V1 = P2*V2
Thus;
P2 = P1*V1/V2
= (1.2 atm)(0.25 L)/(0.125 L)
<u> = 2.4 atm</u>
Answer: Option (D) is the correct answer.
Explanation:
An electric circuit works well when all the connections are complete but if any of the connections in the circuit is loose or disconnected then it is possible that current will not flow from the circuit.
Therefore, when Jenna removed one of the clips on the battery then circuit becomes incomplete and as a result there will no flow of current.
Thus, we can conclude that the electrical energy would stop because the circuit is incomplete.
Answer:
Adolescence is a time of significant growth and development inside the teenage brain. The main change is that unused connections in the thinking and processing part of your child's brain (called the grey matter) are 'pruned' away. ... The front part of the brain, the prefrontal cortex, is remodelled last.
Avagadros constant states that 1 mol of any substance is made of 6.022 x 10^23 units.
These units could be atoms making up elements or molecules making up compounds.
1 mol of molecular oxygen (O2) is made of 6.022 x 10^23 molecules of O2
The mass of 1 mol of O2 is 32 g/mol
This means that the number of oxygen molecules in 32 g are 6.022 x 10^23 molecules
Therefore in 7.36 g of oxygen gas there are - 6.022 x 10^23 /32 g/mol x 7.36 g = 1.39 x 10^23 oxygen molecules
Answer is 1.39 x 10^23 oxygen molecules
