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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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3 years ago

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Explain why copper is used for the roofs of some buildings and magnesium is not.

Scrat [10]

Answer:

Because of the less reactivity of copper.

Explanation:

As well as being resistant to the elements and thereby less likely to be affected by rainfall, hail, and mildew than other types of roofing, copper is also one of the most fireproof materials available. Copper is also highly resistant to thermal changes and thereby doesn't deteriorate quickly.

Magnesium would also corrode PDQ. Magnesium sheeting would also pose an unacceptably high fire hazard.

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2 years ago

Two methanol-water mixtures are contained in separate tanks. The first mixture contains 40.0 wt% methanol and the second contain

RoseWind [281]

Answer:

$M_{per}= 52.86$

$W_{per}=47.14$

Explanation:

First mixture:

40 wt% methanol - 60 wt% water 200 kg

$m_{met1}=200 kg * 0.4= 80 kg$

$m_{wat1}=200 kg * 0.6= 120 kg$

Second mixture:

70 wt% methanol - 30 wt% water 150 kg

$m_{met2}=150 kg * 0.7= 105 kg$

$m_{wat2}=150 kg * 0.3= 45 kg$

Final mixture:

$m_{metF=80 kg + 105 kg= 185 kg$

$m_{watF}=120 kg + 45 = 165 kg$

$M_{per}=\frac{185 kg}{185 kg + 165 kg}*100= 52.86$

$W_{per}=\frac{165 kg}{185 kg + 165 kg}*100=47.14$

If, the compositions are constant, the only variables are the mass of each mixture used in the final one, so there can be only one independent balance.

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3 years ago

True or False: A property is a way to

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Answer:

True

Explanation:

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2 years ago

Determine the oxidation number of sodium in Na202

Olegator [25]

Answer:

Explanation:

Na₂O₂

NOTE: the oxidation number of oxygen is always –2 except in peroxides where it is –1.

Thus, we can obtain the oxidation number of sodium (Na) in Na₂O₂ as illustrated below:

Na₂O₂ = 0 (oxidation number of ground state compound is zero)

2Na + 2O = 0

O = –1

2Na + 2(–1) = 0

2Na – 2 = 0

Collect like terms

2Na = 0 + 2

2Na = 2

Divide both side by 2

Na = 2/2

Na = +1

Thus, the oxidation number of sodium (Na) in Na₂O₂ is +1

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3 years ago