Answer:
t = 7.58 * 10¹⁹ seconds
Explanation:
First order rate constant is given as,
k = (2.303
/t) log [A₀]
/[Aₙ]
where [A₀] is the initial concentraion of the reactant; [Aₙ] is the concentration of the reactant at time, <em>t</em>
[A₀] = 615 calories;
[Aₙ] = 615 - 480 = 135 calories
k = 2.00 * 10⁻²⁰ sec⁻¹
substituting the values in the equation of the rate constant;
2.00 * 10⁻²⁰ sec⁻¹ = (2.303/t) log (615/135)
(2.00 * 10⁻²⁰ sec⁻¹) / log (615/135) = (2.303/t)
t = 2.303 / 3.037 * 10⁻²⁰
t = 7.58 * 10¹⁹ seconds
NH4+ and NH3 are an acid-conjugate base pair, since NH4+ is an acid, while NH3 is its conjugate base (since it is without the H+).
H2O and H3O+ can also be considered an acid-conjugate base pair, since H3O+ is an acid, while H2O would be its conjugate base. (But if only 1 answer is to be selected, it should be the NH4+ and NH3)
NH4+ and H3O+ are both acids, and both H2O and NH3 can be considered bases.
There are 1.48 × 10²⁵ molecules of zinc oxide in a 2 kg sample. Details about number of molecules can be found below.
<h3>How to calculate number of molecules?</h3>
The number of molecules of a substance can be calculated by multiplying the number of moles of the substance by Avogadro's number.
According to this question, there are 2000g of ZnO in a sample. Zinc oxide has a molar mass of 81.38 g/mol.
no of moles = 2000g ÷ 81.38g/mol
no of moles = 24.57mol
number of molecules = 24.57 × 6.02 × 10²³
number of molecules = 147.95 × 10²³
Therefore, there are 1.48 × 10²⁵ molecules of zinc oxide in a 2 kg sample.
Learn more about number of molecules at: brainly.com/question/11815186
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Answer:
Transition metals, alkali metals, alkaline earth metals Transition metals - Middle of the periodic chart, only average reactivity. alkali metals - As mentioned above, very reactive. Bad choice, going from lower reactivity to higher reactivity.
Hope this answer is right!
