The correct answers are options C, that is, silver tarnishes and becomes black when exposed to oxygen, and option E, that is, diesel fuel burns when it is heated.
Chemical changes refer to the modifications in which the chemistry at molecular level is modified as the initial substance gets transformed into a new and different final substance. This change occurs with the dissociation of old bond and production of new bonds respectively.
Silver gets tarnished and becomes black when exposed to oxygen. This refers to a chemical change as silver a white and lustrous substance gets transformed into a tarnish black final substance. However, silver does not easily react with oxygen at usual circumstances. It easily reacts with sulfur comprising components in the air and generates black compound as Ag₂S.
Burning of diesel fuel when it is heated. Diesel refers to a mixture of hydrocarbons varying approximately from C₁₀H₂₀ to C₁₅H₂₈. When these hydrocarbons get burnt they generate novel substances, that is, carbon dioxide and water. Hence, it is also a chemical reaction.
Answer:
0.00840
Explanation:
The computation of the mole fraction is as follow:
As we know that
Molar mass = Number of grams ÷ number of moles
Or
number of moles = Number of grams ÷ molar mass
Given that
Number of moles of CaI2 = 0.400
And, Molar mass of water = 18.0 g/mol
Now Number of moles of water is
= 850.0 g ÷ 18.0 g/mol
= 47.22 mol
And, Total number of moles is
= 0.400 + 47.22
= 47.62
So, Molar fraction of CaI2 is
= 0.400 ÷ 47.62
= 0.00840
Answer:
The energy levels in an atom are similar to the rungs of a ladder, but they get closer together as they get farther from the nucleus. For an electron to move from one energy level to the next higher level, it must gain the right amount of energy. If less than that amount is available, the electron stays where it is.
Explanation:
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Answer: Option (c) is the correct answer.
Explanation:
Wood is a mixture of different substances. Primarily it consists of cellulose, lignin, water etc.
When we heat wood then all these substance oxidize into the atmosphere even before they could melt.
Whereas iron, sodium chloride and ethanol all are the substances which can melt at any temperature.
Thus, we can conclude that out of the given options, wood, a mixture of different substances is a material that does not melt at any temperature.
