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2 years ago

Chalk markings cannot be easily rubbed off from a black board if kept for a long time.why?

Chemistry

1 answer:

snow_tiger [21]2 years ago

3 0

The chalk particles embed themselves into the small pores on the surface.

Although a chalkboard seems smooth to the touch, it is quite rough at the microscopic level, with pores that reach below the surface.

When you drag chalk across the board, friction causes small particles of chalk to rub off onto the surface.

If you leave the markings for a long time, some of the chalk particles will work their way into the pores.

A brush will remove the surface particles, but it will not be able to get at the particles in the pores.

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In what type of reaction will an acid and a base react with each other

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When an acid and a base are placed together, they react to neutralize the acid and base properties, producing a salt. The H(+) cation of the acidcombines with the OH(-) anion of the base to form water.

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Fusion releases less energy than fission

fusion most commonly combines heavy isotopes of hydrogen into helium.

Explanation:

Nuclear fusion is a form of reaction that involves the combination of two light nuclei to form one that is heavier in mass.

The other form is nuclear fission which is the splitting of heavier nuclei either spontaneously or when bombarded with other nuclei.

Nuclear fusion reactions in the core of stars powers the universe.
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Small nuclei are involved in nuclear fusion and not the large ones.
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2 years ago

The student ran out of time and did not do the second heating. Explain how this error would affect the calculation for the numbe

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The error caused will lower the number of moles when he did not do the second heating.This question is related to the empirical formula.

<h3>What is Empirical formula ?</h3>

A formula giving the proportions of the elements present in a compound but not the actual numbers or arrangement of atoms.

The empirical formula is the simplest ratio of atoms in a given compound.

we know that heating is used to eliminate most of the water molecules which are attached to the compound in the question, it's given that the second heating was not performed by the students.

This means that there are still some water molecules attached to the compound. This will imply that higher mass will be calculated for the compound because the water molecules are also considered.

So now, if we look at the calculation for the number of moles of water in this, we can say that this will be lower than the actual amount.

This is because there are some unaccounted moles of water which are still attached to the compound and these will be accounted in the compound mass rather than the waters. Therefore, the number of moles will be lower.

Hence, The error caused will lower the number of moles when he did not do the second heating.

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