Answer:
Kc for this reaction is 0.06825
Explanation:
Step 1: Data given
Number of moles formaldehyde CH2O = 0.055 moles
Volume = 500 mL = 0.500 L
At equilibrium, the CH2O(g) concentration = 0.051 mol
Step 2: The balanced equation
CH2O <=> H2 + CO
Step 3: Calculate the initial concentrations
Concentration = moles / volume
[CH2O] = 0.055 moles . 0.500 L
[CH2O] = 0.11 M
[H2] = 0M
[CO] = 0M
Step 4: The concentration at the equilibrium
[CH2O] = 0.11 - X M = 0.051 M
[H2] = XM
[CO] = XM
[CH2O] = 0.11 - X M = 0.051 M
X = 0.11 - 0.051 = 0.059
[H2] = XM = 0.059 M
[CO] = XM = 0.059 M
Step 5: Calculate Kc
Kc = [H2][CO]/[CHO]
Kc = (0.059 * 0.059) / 0.051
Kc = 0.06825
Kc for this reaction is 0.06825
Answer:The correct answer is option (C).
Explanation:

After the reaction between Zinc and copper(II) chloride, Zinc chloride and copper will be obtained as a product. This reaction occurs because zinc is more reactive than copper which displaces the copper from its aqueous solution.
The student will expect to find copper metal at bottom of the beaker with aqueous solution of zinc chloride.
Hence the correct answer is option (C).
Answer: 
Explanation:
According to the law of conservation of mass, mass can neither be created nor be destroyed. Thus the mass of products has to be equal to the mass of reactants. The number of atoms of each element has to be same on reactant and product side. Thus chemical equations are balanced.
Thus in the reactants, there are 2 atoms of hydrogen and 2 atoms of iodine .Thus there has to be 2 atoms of hydrogen and 2 atoms of iodine in the product as well. Thus a coefficient of 2 is placed in front of HI.
The balanced chemical reaction is:

An orbital that penetrates into the region occupied by core electrons is less shielded from nuclear charge than an orbital that does not penetrate and therefore has a lower energy.
Explanation:
The only true statement from the given options is that "an orbital that penetrates into the region occupied by core electrons is less shielded from nuclear charge than an orbital that does not penetrate and therefore has a lower energy." Inner orbitals which are also known to contain core electrons feels the bulk of the nuclear pull on them compared to the outermost orbitals containing the valence electrons.
- The nuclear pull is the effect of the nucleus pulling and attracting the electrons in orbitals.
- This pull is stronger for inner orbitals and weak on the outer ones.
- The outer orbitals are said to be well shielded from the pull of the nuclear charge.
- Also, based on the quantum theory, electrons in the outer orbitals have higher energies because they occupy orbitals at having higher energy value.
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