What are the four important steps needed to obtain accurate meting points on a mel-temp? select four options:

1. grind the sample into a fine powder.
2. put the smallest amount you can see in a capillary tube.
3. fill the capillary tube with about 3mm of powder.
4. set the voltage to rise quickly to 20 degrees below the expected temperature, then re-adjust so the temp rises at 2 degrees per minute.
5. set the voltage to rise quickly to 20 degrees below the expected temperature, then re-adjust so the temp rises at 10 degrees per minute.
6. record the temp at which liquid first appears and the temp at which the last crystal disappears.
7. record the temp at which the sample completely melts and the temp when it boils.

The four important stages are stage 1,3,4,6

Explanation: in stage 1, it is very important to grind the sample into a fine powder, to increase the surface tension, and to make it possible of entering inside the capillary tube.

In stage 3. It is important to know the amount of sample that should be filled in the capillary. The powdered sample to be filled must be between 2-3mm

In stage 4. The temperature has to be set to rise immediately it is plugged on.

In stage 6. For accurate result, the temperature at which the first melting occurs should be recorded and he temperature at which the last crystal disappear. They are some other cautions to note when using a Mel-Temp to obtain accurate melting point of a substance, as it is not limited to only the four steps above.

it is a good conductor

explanation:

answer: - first one is the correct answer. .

explanations: - potassium sulfide is and cobalt(ii) chloride is .

charge on k is +1, charge on s is -2, charge on co is +2 and charge on cl is -1.

in a double replacement reaction the ion exchange takes place. in general the reaction looks like:

if one of the product is insoluble as per solubility rules then a precipitate of it is formed.

when we mix the aqueous solutions of potassium sulfide and cobalt(ii) chloride then chloride ion goes with potassium ion and sulfide ion goes with cobalt ion and the balanced equation is written as:

k and cl has equal charges, similarly co and s has equal charges and hence no subscripts are used for the product side.

as per the solubility rules, cos is insoluble and so it's precipitate is formed.

looking at the given choices, first choice is correct.