Identify each of the highlighted materials as an element, a compound, or a mixture, and explain your reasoning.
2 answers:
Answer 1) Butane : It is a compound which is made up by combination of elements of carbon and hydrogen together. It contains four carbon atoms which has ten atoms of hydrogen. The bonds between carbon and hydrogen are formed by covalently sharing of electrons. Therefore, butane is a compound.
Answer 2) Benzene : It is also a compound. Benzene contains six molecules of carbon and six molecules of hydrogen. They are covalently bonded with hydrogen atoms around the carbon atoms. It is termed as compound because it cannot be separated chemically.
Answer 3) Gasoline : This is an example of mixture. Gasoline usually contains mixture of many hydrocarbons in the compound state. It consists of mainly hydrocarbons which are between 4 to 12 carbon atoms per molecule (C4 - C12). It is majorly has the mixture of paraffins (which are alkanes), cycloalkanes (which are naphthenes), and olefins (which are alkenes). So, it will be correct to assign the term mixture to gasoline.
Answer 4) Kerosene - It is a mixture. Kerosene is made up of mixture of hydrocarbons. The chemical composition mainly depends on its source, but it usually consists of about ten different hydrocarbons, where each contains ten to sixteen carbon atoms per molecule. Therefore, assigning kerosene as a mixture is correct.
Answer 5) - It is an element. The molecular formula of oxygen is
. Which states that when found in diatomic state the oxygen is stable and can exist freely in nature. The elemental form of oxygen is in the diatomic form. Therefore, oxygen (
) is an element.
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Answer : The correct option is, (B) Salicylic acid
Solution :
First we have to calculate the moles of salicylic acid and acetic anhydride.
Now we have to calculate the limiting and excess reagent.
The balanced chemical reaction is,
From the balanced reaction we conclude that
As, 2 moles of salicylic acid react with 1 mole of acetic anhydride
So, 0.507 moles of salicylic acid react with mole of acetic anhydride
The excess of acetic anhydride = 0.783 - 0.2535 = 0.5295 moles
That means the in the given balanced reaction, salicylic acid is a limiting reagent because it limits the formation of products and acetic anhydride is an excess reagent.
Hence, the limiting reagent is, salicylic acid.