Stoichiometry problems which give a known amount of one reactant and solve for an amount of product frequently state that there is "an excess" or "plenty" of the reactant(s) not given. (For example, in the equation 2Na + 2H2O → 2NaOH + H2, how many grams of sodium hydroxide are produced from 3.0 mol of sodium with an excess of water?) Why is it necessary to know that there is an excess of these reactant(s)?
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Related Questions
Which process results in the release of energy stored in the products of photosynthesis?A. polymer synthesisB. depolymerizationC. digestionD. cellular respiration
The main function of the kidney bladder and ureter is-?
Which biogeochemical cycle is the only one that does not include the atmosphere?
If the formic acid were replaced with a strong acid such as HCI at the same concentration (2.0 M). how would that change the volume needed to reach the equivalence point? (A) The change would reduce the amount, as the acid now fully dissociates. (B) The change would reduce the amount, because the base will be more strongly attracted to the acid. (C) The change would increase the amount, because the reaction will now go to completion instead of equilibrium. (D) Changing the strength of the acid will not change the volume needed to reach equivalence.
a large amount of solvent and a small amount of solute
a large amount of solute and a small amount of solvent
a high density value for the solution
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is this?
This is a conversion.
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Answer:
Explanation:
Given
Required
Convert to meters per minutes
Start by converting the speed from miles to meters
So, we have:
Next, we convert time from hours to minutes
So, we have:
Hence, the equivalent of 25 miles per hour is 670.56 meters per minutes
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Answer:
A carbon-14 atom has 6 protons, 8 neutrons and 6 electrons. The number 12 or 14 in the name of carbon-12 and carbon-14 refers to their atomic mass.
Explanation:
Those atoms that have the same "atomic number" but differente "atomic mass" (or atomic weight) are called isotopes.
Atomic number indicates the amount of electrons that an atom has, which matchs with the number of protons it has.
Atomic mass indicates the sum of protons and neutrons that an atom has.
Example with carbon-12:
carbon atomic number = 6 (find this information in a periodic table)
electrons= 6
protons= 6
carbon atomic mass = 12 (find this information in a periodic table)
neutrons= atomic mass - number of protons= 12-6 = 6 neutrons
Using the same analysis for carbon-14:
carbon atomic number = 6
electrons= 6
protons= 6
carbon atomic mass = 14
neutrons= atomic mass - number of protons = 14-6 = 8 neutrons
In this way, carbon-14 is an isotope of carbon-12 because carbon-14 has the same atomic number than carbono-12 but different atomic mass.
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Final answer:
An excited state electron configuration of Gallium (Ga) might be [Ar] 4s2 3d9 4p2, as this configuration represents an electron having absorbed energy and moved from the 3d to the 4p level.
Explanation:
The electron configuration of an atom in its ground state is the arrangement of electrons in the lowest possible energy levels (the 'normal' arrangement). For the element Gallium (Ga), the ground state electron configuration is [Ar] 4s2 3d10 4p1. However, when an atom is in an excited state, one or more electrons have absorbed energy and moved to a higher energy level. An electron configuration for an excited state of Gallium might look like [Ar] 4s2 3d9 4p2 as an electron from the 3d level has absorbed energy and moved to the higher 4p level.
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Answer:
-196 kJ
Explanation:
By the Hess' Law, the enthalpy of a global reaction is the sum of the enthalpies of the steps reactions. If the reaction is multiplied by a constant, the value of the enthalpy must be multiplied by the same constant, and if the reaction is inverted, the signal of the enthalpy must be inverted too.
2S(s) + 3O₂(g) → 2SO₃(g) ΔH = -790 kJ
S(s) + O₂(g) → SO₂(g) ΔH = -297 kJ (inverted and multiplied by 2)
2S(s) + 3O₂(g) → 2SO₃(g) ΔH = -790 kJ
2SO₂(g) → 2S(s) + 2O₂(g) ΔH = +594 kJ
-------------------------------------------------------------
2S(s) + 3O₂(g) + 2SO₂(g) → 2SO₃(g) + 2S(s) + 2O₂(g)
Simplifing the compounds that are in both sides (bolded):
2SO₂(g) + O₂(g) → 2SO₃(g) ΔH = -790 + 594 = -196 kJ
Final answer:
The enthalpy of the reaction where sulfur dioxide is oxidized to sulfur trioxide is -395 kJ.
Explanation:
The calculation of the enthalpy change of the reaction in which sulfur dioxide is oxidized to sulfur trioxide involves Hess's Law, which states that the enthalpy change of a chemical reaction is the same whether it takes place in one step or several steps. This can be solved by comparing the enthalpy changes given in the two reactions presented.
First, consider the reactions given:
2S(s) + 3O₂(g) → 2SO₃(g), ΔH = -790 kJ
S(s) + O₂(g) → SO₂(g), ΔH = -297 kJ
From these reactions, it is seen that the first reaction can be re-written as:
2SO₂(g) + O₂(g) → 2SO₃(g), ΔH = -790 kJ
However, this reaction contains two moles of SO₂ whereas the reaction in question only requires one mole. Thus, the enthalpy change for the reaction becomes: ΔH = -790 KJ / 2 = -395 kJ.
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