Answer: 0.5 moles
Explanation:
Cr2(SO3)2 is the chemical formula for chromium sulphate.
Given that,
Amount of moles of Cr2(SO3)2 (n) = ?
Mass of Cr2(SO3)2 in grams = 128.9g
For molar mass of Cr2(SO3)2, use the atomic masses:
Chromium, Cr = 52g;
Sulphur, S = 32g;
Oxygen, O = 16g
Cr2(SO3)2 =
(52g x 2) + [(32g + 16g x 3) x 2]
= 104g + [(32g + 48g) x 2]
= 104g + [80g x 2]
= 104g + 160g
= 264g/mol
Since, n = mass in grams / molar mass
n = 128.9g / 264g/mol
n = 0.488 mole [Round the value of n to the nearest tenth which is 0.5
Thus, there are 0.5 moles in 128.9 grams of Cr2(SO3)2
Particles of gas are more scarcely placed as compared to that of liquid.
the intermolecular forces will be less in gaseous state and hence is less stable
The colored light emitted is energy and in order to emit energy the element should first obtain energy. The energy absorbed by the substance can be in the form of radiation, heat or electricity. Hope this answers the question. Have a nice day.
Explanation:
Elements that belong to same group contains same number of valence electrons. Hence, they tend to show similar chemical properties.
When we move across a period then number of electrons get added to the same shell. As a result, there will be no increase in size of elements.
Also, metals are the elements that belong to group 1, 2 and d-block elements are also known as metals. Metallic character of elements decreases when we move left to right in a periodic table.
As most reactive metals are placed on the left side of periodic table.
Since, size of elements increases on moving down the group. So, an element is able to easily lose its valence electrons because of less force of attraction between its nucleus and valence electrons.
As a result, there will be increase in reactivity of metals on moving down the group.
Thus, we can conclude that given sentences are as follows.
- Elements in the same group have the same number of valence electrons.
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Elements in the same period have the same number of electron shells.
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Metallic elements become less reactive as you move left to right in a period.
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Metallic elements become more reactive as you move top to bottom in a group.