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3 years ago

How many moles of oxygen are in 25.45 g of caco3?

1 answer:

3 0

From the periodic table:
mass of oxygen = 16 grams
mass of calcium = 40 grams
mass of carbon = 12 grams
mass of CaCO3 = 40 + 12 + 3(16) = 100 grams
Therefore, each 100 grams of CaCO3 contains 3 moles of oxygen
To know the number of oxygen moles in 25.45 grams, we will simply do cross multiplication as follows:
number of oxygen moles = (25.45 x 3) / 100 = 0.7636

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Which of the following is an example of a chemical change?

alexdok [17]

Answer:

Dissolving sugar in water, burning paper, and melting gold are all chemical changes

Explanation:

The action cannot be reversed, or undone. Therefore it is a chemical change.

Boiling water is a physical change.

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3 years ago

a water sample is found to have a cl- content of 100ppm as nacl what is the concentration of chloride in moles per liter

ladessa [460]

Answer:

The concentration of chloride ion is $2.82\times10^{-3}\;mol/L$

Explanation:

We know that 1 ppm is equal to 1 mg/L.

So, the $Cl^-$ content 100 ppm suggests the presence of 100 mg of $Cl^-$ in 1 L of solution.

The molar mass of $Cl^-$ is equal to the molar mass of Cl atom as the mass of the excess electron in $Cl^-$ is negligible as compared to the mass of Cl atom.

So, the molar mass of $Cl^-$ is 35.453 g/mol.

Number of moles = (Mass)/(Molar mass)

Hence, the number of moles (N) of $Cl^-$ present in 100 mg (0.100 g) of $Cl^-$ is calculated as shown below:

$N=\frac{0.100\;g}{35.453\;g/mol}=2.82\times 10^{-3}\;mol$

So, there is $2.82\times10^{-3}\;mol$ of $Cl^-$ present in 1 L of solution.

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4 years ago

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Read 2 more answers

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The answer is a. Chemical change.

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