Answer:
5.0 x 10⁹ 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 K-40 = 1.251 × 10⁹ 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/(1.251 × 10⁹ years) = 5.54 x 10⁻¹⁰ 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 = 5.54 x 10⁻¹⁰ year⁻¹).
t is the time of the reaction (t = ??? year).
[A₀] is the initial concentration of (K-40) ([A₀] = 100%).
[A] is the remaining concentration of (K-40) ([A] = 6.25%).
∴ (5.54 x 10⁻¹⁰ year⁻¹)(t) = ln((100%)/( 6.25%))
∴ (5.54 x 10⁻¹⁰ year⁻¹)(t) = 2.77.
∴ t = 2.77/(5.54 x 10⁻¹⁰ year⁻¹) = 5.0 x 10⁹ years.
Speed (m/s) = distance (metres) ÷ time (seconds)
For Track 1: 0.2 ÷ 2 = 0.1m/s
For Track 2: 0.2 ÷ 2 = 0.1m/s
For Track 3: 0.6 ÷ 6 = 0.1m/s
For Track 4: 0.4 ÷ 6 = 0.07m/s
The train on Track 4 had the slowest speed because it's got the shortest speed and it's covering less distance per second therefore it is slower.
Answer:
<u>3</u>KClO4 + KCl ➡️ <u>4</u>KClO3
<u>2</u>AlI3 + <u>3</u>HgCl2 ➡️ <u>2</u>AlCl3 + <u>3</u>HgI2
Answer:
Explanation:
Surface tension allows the coin to float on top of the water in this glass. The strong cohesion between the molecules makes it harder for objects on the surface of the water to sink.
Answer: When heat is added to a substance, the molecules and atoms vibrate faster. As atoms vibrate faster, the space between atoms increases. The motion and spacing of the particles determines the state of matter of the substance. The end result of increased molecular motion is that the object expands and takes up more space.
Explanation: Hope this helps!