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>
Answer:
8
Explanation:
The atomic mass of an atom refers to the number of protons in the nucleus of an atom. Hence, an element with 6 valence electron mean that it has 6 electrons in its outermost shell.
The atomic Number of elements with 6 valence electrons cannot necessarily be the same, however, elements with 6 valence electrons belong to group six on the periodic table.
From the options given above, :
Atomic number of 8 :
Configuration : 2, 6
Atomic number of 10 :
Configuration : 2, 8
Atomic number of 12 :
Configuration : 2, 8, 2
Hence, only the element with atomic number of 8 has 6 valence electrons in its outer most shell, hence, the answer.
Explanation:
The difference among mRNA, tRNA and rRNA are:
mRNA: It carries DNA's protein building information from nucleus to the cytoplasm. It is also read as codons nucleotide triplet that indicate specific amino acids .
rRNA: The function of rRNA is to join amino acids to the peptide bonds.
tRNA: Delivers amino acids to the site of protein synthesis. It also has an anticodon that interact with specific codon of another nucleus.
The similarity among mRNA, rRNA and tRNA is that they all consists of ribonucleic acid and can exist outside the nucleus in eukaryotes.
It’s A .. I think I hope this helps !
Answer: 6.022×1023
Explanation: Chemists generally use the mole as the unit for the number of atoms or molecules of a material. One mole is equal to 6.022×1023 molecular entities and each element has a different molar mass depending on the weight of 6.022×1023 of its atoms (1 mole)