Answer:
3,964 years.
Explanation:
- It is known that the decay of a radioactive isotope isotope obeys first order kinetics.
- Half-life time is the time needed for the reactants to be in its half concentration.
- If reactant has initial concentration [A₀], after half-life time its concentration will be ([A₀]/2).
- Also, it is clear that in first order decay the half-life time is independent of the initial concentration.
- The half-life of the element is 5,730 years.
- For, first order reactions:
<em>k = ln(2)/(t1/2) = 0.693/(t1/2).</em>
Where, k is the rate constant of the reaction.
t1/2 is the half-life of the reaction.
∴ k =0.693/(t1/2) = 0.693/(5,730 years) = 1.21 x 10⁻⁴ year⁻¹.
- Also, we have the integral law of first order reaction:
<em>kt = ln([A₀]/[A]),</em>
where, k is the rate constant of the reaction (k = 1.21 x 10⁻⁴ year⁻¹).
t is the time of the reaction (t = ??? year).
[A₀] is the initial concentration of the sample ([A₀] = 100%).
[A] is the remaining concentration of the sample ([A] = 61.9%).
∴ t = (1/k) ln([A₀]/[A]) = (1/1.21 x 10⁻⁴ year⁻¹) ln(100%/61.9%) = 3,964 years.
Answer:
32 g Cu
Explanation:
1 mol Cu -> 63.5 g
0.5 mol Cu ->x
x=(0.5 mol *63.5 g)/1 mol x= 32 g Cu
1 - causes the molecules of the object or surface it strikes to vibrate faster, increasing its temperature.
2-carbon dioxide, methane, nitrous oxide, and water vapor it has to be one of these 3
3-The greenhouse effect is the way in which heat is trapped close to Earth's surface by “greenhouse gases.”
4- because of the fossil fuels that people are burning for energy.
5- due to human activities
Answer:
0.185moles
Explanation:
Given parameters:
Volume of O₂ = 49.8L
Unknown:
Number of moles of sucrose required = ?
Solution:
We can assume that the reaction takes place at standard temperature and pressure.
From this, we can find the number of moles of oxygen that reacted and extrapolate to that of sucrose.
Chemical equation;
C₁₂H₂₂0₁₁ + 120₂ → 12CO₂ + 11H₂0
Number moles = 
at STP
Number of moles of oxygen gas = 
= 2.22moles
12 moles of oxygen gas combines with 1 mole of sucrose
2.22 moles of oxygen gas will combine with 
= 0.185moles
