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3 years ago

Which substance has Hf defined as 0 kJ/mol? H2O (s) Ne (l) O2 (g) CO2 (g)

Chemistry

2 answers:

vlabodo [156]3 years ago

8 0

Answer:

O₂ (g).

Explanation:

All elements that found in nature has heat of formation (Hf) equal 0 J/mol.

So, the substance that has heat of formation (Hf) equal 0 J/mol is O₂ (g).

H₂O is formed from the reaction of hydrogen and oxygen and has Hf, Also, the solidification of H₂O (s) from H₂O (l) has (Hf).

Although, Ne (g) is found in nature and has no Hf, the liquification to form Ne (l) has heat of formation (Hf).

CO₂ (g) is formed from the reaction between carbon and oxygen and so has heat of formation (Hf).

Crazy boy [7]3 years ago

4 0

Answer:

O2 (g)

Explanation:

Took the test

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Answer:

2.05*10⁻⁵ moles of CF₂ can dissolve in 100 g of water.

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Explanation:

First, by definition of solubility, in 100 g of water there are 0.0016 g of CaF₂. So, to know how many moles are 0.0016 g, you must know the molar mass of the compound. For that you know:

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$moles=\frac{0.0016 grams*1 mole}{78 grams}$

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$mass of CaF_{2}=\frac{1000 mL*1g}{1mL}$

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Now you can apply the following rule of three: if there are 78 grams of CaF₂ in 1 mole, in 1000 grams of the compound how many moles are there?

$moles=\frac{1000 grams*1 mole}{78 grams}$

moles=12.82

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