14
15
147.5
Answer: The sample must have passed 4 half-lives after the sample was originally formed.
Explanation: This is a type of radioactive decay and all the radioactive process follow first order kinetics.
Equation for the reaction of decay of radioisotope follows:
To calculate the initial amount of , we will require the stoichiometry of the reaction and the moles of the reactant and product.
Expression for calculating the moles is given by:
Moles of left =
Moles of
By the stoichiometry of above reaction,
1 mole of is produced by 1 mole
So, 0.7429 moles of will be produced by =
Amount of decomposed will be = 0.7429 moles
Initial amount of will be = Amount decomposed + Amount left = (0.0495 + 0.7429)moles = 0.7924 moles
Now, to calculate the number of half lives, we use the formula:
where,
a = amount of reactant left after n-half lives = 0.0495 moles
= Initial amount of the reactant = 0.7924 moles
n = number of half lives
Putting values in above equation, we get:
Taking log on both sides, we get
Answer:
4
Explanation:
Edg 2020
Answer:
the change in internal energy per mole of sucrose is 5989 KJ/mol
Explanation:
Since the calorimeter is a bomb calorimeter , where the volume remains constant
ΔE= Qrx
And assuming no heat losses to the surroundings
Qv + Qrx = 0
Cc*ΔT - Qrx = 0 ,
Qrx = Cc * ΔT = 7.50 KJ/°C * 22 °C = 165 KJ
the change in internal energy is calculated dividing by the number of sucrose moles involved n. the molecular weight of sucrose is
Mw= 12* 12g/mol + 22* 1g/mol + 11* 16 g/mol = 342 g/mol
n = m / Mw = 10 g / 342 g/mol = 0.029 mol
the change in internal energy per mole of sucrose is
Δe= ΔE/n = 165 KJ/0.029 mol = 5989 KJ/mol
Answer:
its a) the rate of decay is constant.