To dissolve a 3.94g copper penny, we would need approximately 331 milliliters of 1.50 M HNO3, taking into consideration the stoichiometry of the copper-nitric acid reaction.
Stoichiometry is required to solve this chemistry problem. The balanced equation for the reaction between copper and nitric acid is: 3Cu(s) + 8HNO3(aq) → 2NO(g) + 3Cu(NO3)2(aq) + 4H2O(l)
From this, we can conclude that every mole of copper reacts with eight moles of nitric acid. The molecular weight of copper is approximately 63.546 g/mole, so the moles of copper in an old penny can be calculated by mass (3.94 g) divided by the molar mass (63.546 g/mol).
This calculation shows that there are approximately 0.062 moles of copper in a penny. Since we determined that eight moles of nitric acid are required to react with one mole of copper, eight times the moles of copper gives the moles of nitric acid required, which is 0.496 moles.
Since molarity (M) = moles/liters, we can find out the volume of 1.50 M HNO3 required by rearranging the formula to be Liters= moles/Molarity. So, 0.496 moles divided by 1.50 M gives roughly 0.331 liters, which can be converted to approximately 331 milliliters.
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light with any intensity above a certain frequency
light with any frequency below a certain intensity
light with any frequency above a certain intensity
The correct answer: (b) light with any intensity above a certain frequency
The explanation:
when Energy of a photon : E = hf
- The photoelectric effect works like this:
- If you shine light of high enough energy on to a metal, electrons will be emitted from the metal. Light below a certain threshold frequency, no matter how intense, will not cause any electrons to be emitted. Light above the threshold frequency, even if it's not very intense, will always cause electrons to be emitted.
Answer:
b
Explanation:
b. 4
c. 8
d. 10
e. 13
B. c-14
C. u-235
D. u-238
Answer:
C. U-235
Explanation:
A fission reaction is one in which an unstable radioisotope breaks down into smaller nuclei when bombarded with energetic particles.
The highly unstable isotope that is often used in fission reactions is U-235. When bombarded with neutrons that atom breaks down to form krypton and barium along with the release of a large amount of energy. The reaction is given as:
₉₂U²³⁵ + ₀n¹ → ₃₆Kr⁸⁹ + ₅₆Ba¹⁴⁴ + 3₀n¹ + 210 Mev energy
B) Platinum
C) Promethium
D) Carbon
b. An atom must be identical in size.
c. An atom must be similar in size.
d. The substituting atom must be from the same period. E) The substituting atom must be from the same group.
The correct answer is options c and e.
A solid solution is basically a multi-component framework that comprises a mixture of two or more elements exhibiting a similar crystal lattice. The examples of solid solutions are alloys.
The requirements for one kind of atom to substitute for another in a solid solution are:
1. The size of the atom must be similar.
2. The substituting atom must be from a similar group.
Answer:
An atom must be similar in size.
The substituting atom must be from the same group.
Explanation:
A solid solution is a solid mixture containing a minor component uniformly distributed within the crystal lattice of another component called the major component. Metal alloys are typical examples of a solid solution.
Note that only atoms of similar size can substitute each other in a solid solution. Usually atoms of elements in the same group have atomic sizes that vary within narrow ranges. Hence atoms of elements in the same group have similar atomic sizes and can substitute each other in a solid solution.