Answer is: 1/16 of the original mass remains unchanged after 10 years
Take 100 atoms:
After first half-life (2.5 years): 50% · 100 ÷ 100% = 50 or 1/2.
After second half-life (5 years): 0.5 · 50 = 25 or 1/4.
After third half-life (7.5 years): 0.5 · 25 = 12.5 or 1/8.
After fourth half-life (10 years): 0.5 · 12.5 = 6.25 or 1/16.
6.25 ÷ 100 · 100% = 6.25% or 1/16.
A. What life may have been like before the evoltuon of photosynthesis
It has bent geometry, which is similar to H2O, with the same angle of 109.5 degrees between 2 single H-S bonds.
Answer:
Aluminum metal
Explanation:
In order to properly answer this or a similar question, we need to know some basic rules about galvanic cells and standard reduction potentials.
First of all, your strategy would be to find a trusted source or the table of standard reduction potentials. You would then need to find the half-equations for aluminum and gold reduction:
Since we have a galvanic cell, the overall reaction is spontaneous. A spontaneous reaction indicates that the overall cell potential should be positive.
Since one half-equation should be an oxidation reaction (oxidation is loss of electrons) and one should be a reduction reaction (reduction is gain of electrons), one of these should be reversed.
Thinking simply, if the overall cell potential would be obtained by adding the two potentials, in order to acquite a positive number in the sum of potentials, we may only reverse the half-equation of aluminum (this would change the sign of E to positive):
Notice that the overall cell potential upon summing is:
Meaning we obey the law of galvanic cells.
Since oxidation is loss of electrons, notice that the loss of electrons takes place in the half-equation of aluminum: solid aluminum electrode loses 3 electrons to become aluminum cation.
Answer:
The answer to your question is 2.92 x 10⁻⁶ g
Explanation:
Data
mass of K = ?
atoms of K = 4.50 x 10¹⁶
Process
To answer this question just remember that the atomic mass of any element is equivalent to Avogadro's number.
1.- Look for the atomic number of Potassium
Atomic number = 39.10 g
2.- Use proportions and cross multiplication
39.10 g of K --------------- 6.023 x 10²³ atoms
x ----------------4.50 x 10¹⁶ atoms
x = (4.50 x 10¹⁶ x 39.10) / 6.023 x 10²³
-Simplify
x = 1.7595 x 10¹⁸ / 6.023 x 10²³
-Result
x = 2.92 x 10⁻⁶ g