The volume of a block of lead metal that has a density of 11.3g/mL and weighs 2.10g is 0.186mL.
<h3>How to calculate volume?</h3>
The volume of a substance can be calculated by dividing the mass of the substance by its density. That is;
Volume = mass ÷ density
According to this question, a chemist has a block of lead metal (density is 11.3 g/mL). The block weighs 2.10g.
Volume = 2.10g ÷ 11.3g/mL
Volume = 0.186mL
Therefore, the volume of a block of lead metal that has a density of 11.3g/mL and weighs 2.10g is 0.186mL.
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Answer:
% = 76.75%
Explanation:
To solve this problem, we just need to use the expressions of half life and it's relation with the concentration or mass of a compound. That expression is the following:
A = A₀ e^(-kt) (1)
Where:
A and A₀: concentrations or mass of the compounds, (final and initial)
k: constant decay of the compound
t: given time
Now to get the value of k, we should use the following expression:
k = ln2 / t₁/₂ (2)
You should note that this expression is valid when the reaction is of order 1 or first order. In this kind of exercises, we can assume it's a first order because we are not using the isotope for a reaction.
Now, let's calculate k:
k = ln2 / 956.3
k = 7.25x10⁻⁴ d⁻¹
With this value, we just replace it in (1) to get the final mass of the isotope. The given time is 1 year or 365 days so:
A = 250 e^(-7.25x10⁻⁴ * 365)
A = 250 e^(-0.7675)
A = 191.87 g
However, the question is the percentage left after 1 year so:
% = (191.87 / 250) * 100
<h2>
% = 76.75%</h2><h2>
And this is the % of isotope after 1 year</h2>
Energy levels inside an atom are the specific energies that electrons can have when occupying specific orbitals.
