Which statement best describes the light that will cause emission of electrons from a given metal through the photoelectric effect?light with any intensity below a certain frequency
light with any intensity above a certain frequency
light with any frequency below a certain intensity
light with any frequency above a certain intensity
Answers
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:
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Answers
Answer : The correct option is, 318.1 J
Solution :
The given chemical reaction will be,
In this reaction, X and Y are the reactants and W and Z are the products.
As we know that the energy remains conserved during the chemical reaction.
So,
Sum of energy of product = Sum of energy of reactant
Therefore, the amount of chemical energy of product Z contain will be, 318.1 J
Answer:
318.1 J
Explanation:
The reaction given is:
X + Y → W + Z
The chemical energy of the reaction (ΔU), is the variation of the chemical energy, so is the chemical energy of the products (UW and UZ) less the chemical energy of the reactants (UX and UY).
If the reaction loses the chemical energy, it must be negative, and the chemical energy that a substance contains, is positive.
ΔU = (UW + UZ) - (UX + UY)
-111.6 = (41.9 + UZ) - (199.3 +272.3)
-111.6 = 41.9 + UZ - 471.6
- UZ = - 429.27 + 111.6
-UZ = - 318.1
UZ = 318.1 J
Answers
Answer:
Considering the reaction stoichiometry and the definition of limiting reagent, the mass of AlCl₃ that is produced when 10.0 grams of Al₂O₃ react with 10.0 grams of HCl is 12.19 grams.
Explanation:
Al₂O₃ + 6 HCl → 2 AlCl₃ + 3 H₂O
By reaction stoichiometry (that is, the relationship between the amount of reagents and products in a chemical reaction), the following amounts of moles of each compound participate in the reaction:
Al₂O₃: 1 mole
HCl: 6 moles
AlCl₃: 2 moles
H₂O: 3 moles
The molar mass of the compounds present in the reaction is:
Al₂O₃: 102 g/mole
HCl: 36.45 g/mole
AlCl₃: 133.35 g/mole
H₂O: 18 g/mole
Then, by reaction stoichiometry (that is, the relationship between the amount of reagents and products in a chemical reaction), the following amounts of mass of each compound participate in the reaction:
Al₂O₃: 1 mole× 102 g/mole= 102 grams
HCl: 6 moles× 36.45 g/mole= 218.7 grams
AlCl₃: 2 moles× 133.35 g/mole= 266.7 grams
H₂O: 3 moles× 18 g/mole= 54 grams
The limiting reagent is one that is consumed first in its entirety, determining the amount of product in the reaction. When the limiting reagent is finished, the chemical reaction will stop.
To determine the limiting reagent, it is possible to use a simple rule of three as follows: if by stoichiometry 102 grams of Al₂O₃ reacts with 218.7 grams of HCl, 10 grams of Al₂O₃ reacts with how much moles of HCl?
mass of HCl= 21.44 grams
But 21.44 grams of HCl are not available, 10 grams are available. Since you have less moles than you need to react with 10 grams of Al₂O₃ , HCl will be the limiting reagent.
Then, it is possible to determine the mass of AlCl₃ produced by another rule of three: if by stoichiometry 218.7 grams of HCl produce 266.7 grams of AlCl₃, if 10 grams of HCl react how much mass of AlCl₃ will be formed?
mass of AlCl₃= 12.19 grams
In summary, the mass of AlCl₃ that is produced when 10.0 grams of Al₂O₃ react with 10.0 grams of HCl is 12.19 grams.
Answers
0.75 moles H 2CO 3 = 47 g
3.42 moles CO = 84.0 g
Answers
Answer: 3.42 moles CO = 84.0g, is not true.
Explanation:
Moles is given by the formular; Mass / Molar Mass.
Therefore; 0.2 moles O2 = 6g is true when we multiply 32g x 0.2 = 6g approximately.
0.75 moles H2CO3 = 47g.
Molar formular for H2CO3 = 2 + 12 + 48 =62g.
If we multiply 62g (molar mass ) by 0.75moles, it gives us 47g approximately.
3.42 moles CO = 84g
molar mass of CO = 12 + 16 = 28g
Multiply 28g x 3.42 moles = 95.76g, which is not true.
it tends to be more negative across a period
it tends to remain the same across periods
it tends to be more negative down a group
Answers
The answer is it tends to be more negative down a group. This is because as you go down the periodic table, the elements have more electron shells in their atoms. This makes the outermost shells less attracted to the nucleus due to their greater distances from the nucleus. Therefore, these shells are less likely to attract electrons (hence lower electron affinity) and are even more likely to lose electrons from their outer electron orbits.
Answer:
it tends to be more negative across a period
Explanation:
We have to remember that the periodic table is arranged accordingly to the number of electrons that the elements have in their outer valance shell, so the closer you are to the right of the periodic table the closer you get to the elements taht have the most electrons in their outer valance shells, this means that they have a greater negative electron affinity, which means that the elements on the right are more willing to gain an electron.