Chemistry, 05.10.2019 00:30 AlexRavenwood127

Asubstance has a melting point of 80 °c. which of the following is true for the substance?
-when the substance is heated, its temperature will rise above 80 °c after 50% of the liquid has changed to vapors.
-when the substance is heated, its temperature will rise above 80 °c after 100% of the liquid has changed to vapors.
- when the substance is cooled, its temperature will fall below 80 °c after 50% of the liquid has changed to solid.
-when the substance is cooled, its temperature will fall below 80 °c after 100% of the liquid has changed to solid.

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Answer from: kiarasanchez17

When the substance is cooled, its temperature will fall below 80 °C after 100% of the liquid has changed to solid.

Explanation:

Melting point is the temperature at which a solid changes state to liquid. At the melting point, the phase of matter changes from solid state to a liquid flowing state.

If after a substance is cooled, without reaching its melting point, it will still remain as a liquid. Below the melting point the substance will freeze back to its solid state.

For our hypothetical substance whose melting point is 80 °C, it implies that at this temperature, the substance undergoes a phase change from solid to liquid completely. The reverse is also the case, below the melting temperature, all parts of the compound changes back to its original solid state.

Answer from: Quest

answer: - 3.) the oxidation state of nitrogen in no changes from +2 to 0, and the oxidation state of carbon in co changes from +2 to +4 as the reaction proceeds.

solution: - as per the rules, oxidation number of oxygen in its compounds is -2. the sum of oxidation numbers of all the elements of a molecule or compound is zero.

also, the oxidation number in elemental form is zero.

in no, the oxidation number of o is -2 so the oxidation number of n is +2 so that the sum is zero.

similarly, the oxidation number of c in co is +2 and o is -2.

on product side the oxidation number of n is 0 as it is in the elemental form( $n_2$ ) .

oxidation number of c in carbon dioxide is +4 as there are two oxygen in it and we know that each oxygen is -2.

so, oxidation number of n is changing from +2 to 0 and the oxidation number of c is changing from +2 to +4.

since nitrogen is reduced and hence no is acting as an oxidizing agent. carbon is oxidized and so co is acting as a reducing agent.

so, the right choice is number 3.)the oxidation state of nitrogen in no changes from +2 to 0, and the oxidation state of carbon in co changes from +2 to +4 as the reaction proceeds.

Answer from: Quest

answer: $2c_5h_5+1fe\rightarrow 1fe(c_5h_5)_2$

the reaction is type of combination reaction.

explanation:

$? c_5h_5+? fe\rightarrow ? fe(c_5h_5)_2$

on the product side, there are 2 molecules of $c_5h_5$ bonded to fe which means one atom of fe are combined two molecules of $c_5h_5$ . so, balanced chemical equation becomes :

$2c_5h_5+1fe\rightarrow 1fe(c_5h_5)_2$

this reaction follows the reaction type of combination reaction. a combination reaction is defined as chemical reaction in which reactants combines together to form a single product.

$a+b\rightarrow ab$

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Asubstance has a melting point of 80 °c. which of the following is true for the substance?
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