Answer:
0.147 billion years = 147.35 million 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 Potassium-40 is 1.25 billion 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/(1.25 billion years) = 0.8 billion year⁻¹.
- Also, we have the integral law of first order reaction:
<em>kt = ln([A₀]/[A]),</em>
<em></em>
where, k is the rate constant of the reaction (k = 0.8 billion year⁻¹).
t is the time of the reaction (t = ??? year).
[A₀] is the initial concentration of (Potassium-40) ([A₀] = 100%).
[A] is the remaining concentration of (Potassium-40) ([A] = 88.88%).
- At the time needed to be determined:
<em>8 times as many potassium-40 atoms as argon-40 atoms. Assume the argon-40 only comes from radioactive decay.</em>
- If we start with 100% Potassium-40:
∴ The remaining concentration of Potassium-40 ([A] = 88.88%).
and that of argon-40 produced from potassium-40 decayed = 11.11%.
- That the ratio of (remaining Potassium-40) to (argon-40 produced from potassium-40 decayed) is (8: 1).
∴ t = (1/k) ln([A₀]/[A]) = (1/0.8 billion year⁻¹) ln(100%/88.88%) = 0.147 billion years = 147.35 million years.
Answer:
Energy
potential energy kinetic energy
chemical energy thermal energy
joules
Explanation:
chemical energy is a type of potential energy or stored energy. Heat is a kinetic energy and energy is measured in joules.
<span>These are two questions and two answers.
</span>
<span>Question 1) The elements most likely to form more than one type of ion are the ______.
</span>
<span>Answer: option A) transition metals.
</span><span>Jusitification:</span>
<span>
1) The elements form ions by gaining or losing electrons. By gaining electrons, theY form anions (negative iones); by losing electrons, they form cations (positive ions).
</span>
<span>2) The valence shell of the akaly metals is the type ns¹, which means that they have one electron in the valence shell. Then, they only can form one kind of ion which has the configuration of the previous noble gas (n-1)s²(n-1)p⁶ with 1+ charge.
</span>
<span>3) The halogens have valence shell of the type ns²np⁵. That means that easily gain 1 electron to complete the valence shell ns²np₆ (the configuration of the next noble gas), with charge 1-. Gaining 5 electrons or losing more electrons than 1 is very disfavourable, so that is the only kind of ion they form.
</span>
<span>4) The valence shells of alkaline earth metals are of the kind ns². So, the most favourable energetic ion is formed by losing 2 electrons and so taking the configuration of the previous noble gas, with charge 2+. That is the only type of ion they form.
</span>
<span>5) Transition metals have electrons in the orbitals d, which are very similar in energy, and so they might loose 1, 2, or 3, electrons fo form ions with charges 1+, 2+, or 3+ respectively.
</span>
<span>Question 2) The name iron(II) indicates that a compound contains _______.</span>
<span>
A) iron ions with an II+ charge.
</span><span>B) iron ions with a 2+ charge.
</span>
C) iron ions with a negative charge.
<span>D) two types of iron ions.
</span>
Answer: option <span>B) iron ions with a 2+ charge.
</span><span>
</span><span>
</span><span>The oxidation state may be indicated as Roman numerals, in this case II, or as a conventional number with its charge.
</span><span>
</span><span>Iron, a transition metal, may loose 2 or 3 valence electrons. When it loses 2 electrons it forms an ion (cation) with positive charge 2. So, it is iron 2+</span>
Nervous system. Hope this helped