Describe why the formation of sand is a physical change

2 answers:

7 0

In chemical changes new substances are formed and the process is often difficult to reverse. During chemical changes particles do change with atoms or ions regrouping. Bonds between atoms break and new ones form and energy is either given out or taken in. Some chemical changes are initiated by mixing

ValentinkaMS [17]3 years ago

6 0

Most of the sand is made up of loose grains and tiny pieces of worn out and disintegrated rocks. This physical break down of different rocks is termed as weathering.

A physical change happens when the physical form of a substance is altered but it does not transform it into another substance.

Therefore, the formation of sand is only a physical change, and not chemical, because weathering only changes the size of loose fragments of rock that make up the sand.

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How much mass does 0.5 mole of barium contain?

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137.327

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Calcium oxide is used to remove the pollutant SO2 from smokestack gases. The overall reaction is:

fgiga [73]

This problem is providing a chemical reaction reaction at equilibrium and its pressure-based equilibrium constant, and thus asks for molecules of SO2 at equilibrium. At the end, the answer turns out to be 1.25x10¹² molecules.

<h3>Chemical equilibrium</h3>

In chemistry, when chemical reactions take place, they do not necessarily go to completion, but can reach a constant-concentration point denominated "equilibrium" where the reaction does not proceed any longer.

In such a way, for the given reaction, one can write the equilibrium expression based on the law of mass action, which sets the products on top, reactants on bottom and ignores both solids and liquids:

$Kp=\frac{1}{p_{SO_2}*p_{O_2}^{1/2}}$

However, in order to calculate this, one needs the partial pressure of O2, defined in similar problems as 0.21 atm for us to find the partial pressure of SO2 first:

$2.38x10^{15}=\frac{1}{p_{SO_2}*(0.21)^{1/2}}\\\\p_{SO_2}=\frac{1}{(2.38x10^{15})(0.21)^{1/2}}\\\\p_{SO_2}=9.17x10^{-16}atm$

Keep in mind this 0.21 atm may vary depending on the problem you were given.

Thus, we obtain the mole fraction of SO2 as follows:

$x_{SO_2}=\frac{9.17x10^{-16}atm}{9.17x10^{-16}atm+0.21atm}=4.37x10^{-15}\\ \\$

Finally, we use this mole fraction to calculate the moles of SO2 in 475 moles of the gas mixture, and then use the Avogadro's number to calculate the molecules:

$molecules=475mol*4.37x10^{-15}*\frac{6.022x10^{23}}{1mol} =1.25x10^{12}molecules$