Answer:
The mass percent of copper as element is the same.
Explanation:
First of all we need the reaction that is presented below:
→ 
The mass percent of copper (Cu) as element is the same because of during the reaction the element only transform its nature from copper carbonate (
) to copper oxide (
), the latter is a solid and will remain in the system.
On the other hand, you will note that the global percentage mass will be small because of the reaction produce (
) that is a gas and this one will escape for the system.
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The greatest amount of AB would be produced if the equilibrium constant of the reaction is equal to 
. Hence, option D is correct.
<h3>What is an equilibrium constant?</h3>
A number that expresses the relationship between the amounts of products and reactants present at equilibrium in a reversible chemical reaction at a given temperature.
The equilibrium constant expression is a mathematical relationship that shows how the concentrations of the products vary with the concentration of the reactants.
If the value of K is greater than 1, the products in the reaction are favoured. If the value of K is less than 1, the reactants in the reaction are favoured.
Hence, option D is correct.
Learn more about the equilibrium constant here:
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D. powder residues.
the police and forensic chemists usually perform a qualitative test called GPR or gun powder residue. the residue sticks to the skin.
So for D you have to find energy right
from c you get wavelength Lambda
so on D use this
E = Hc / lambda
c is given 1.5 x 10 ^20
h = 6.624 x 10^-34
and then you get answer for energy
