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.
The answer is (1) CaCO3. The bond between C and O is covalent bond. And the bond between Ca2+ and CO3 2- ion is the ionic bond. So the compound CaCO3 satisfy this condition.
Answer:
Explanation:
Glucose = C6H12O6
oxygen = O2
water = H2O
carbon dioxide = CO2
balanced equation :
<em>C6H12O6 (s) + 6 O2 (g) --------------> 6 CO2 (g) + 6 H2O (g)</em>
Answer:
0.278 mol HCl
Explanation:
We currently have 185.0 mL of a 1.50 mol/L solution of HCl. We want to find the number of moles there are.
Based on the given information, our volume is 185.0 mL and our molarity is 1.50. Because molarity is defined as moles / Litre, we can easily find the moles given volume by multiplying molarity by volume.
First, though, we must convert millilitres to litres. There are 1000 mL in 1 L, so divide 185.0 by 1000:
185.0 / 1000 = 0.185 L
Now, multiply 0.185 by 1.50:
0.185 L * 1.50 mol/L = 0.278 mol HCl
Thus the answer is 0.278 mol HCl.
<em>~ an aesthetics lover</em>
D, developing medicine, analyzing compounds and producing new product such as plastic both have to deal with chemistry. Since all need the knowledge of elements, compounds, etc.
