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timurjin [86]
3 years ago
11

How is enthalpy used to predict whether a reaction is endothermic or exothermic?

Chemistry
1 answer:
Dahasolnce [82]3 years ago
8 0
If the enthalpy change is negative, then the reaction is exothermic because heat energy was lost to the surroundings.

If the enthalpy change was positive, then the reaction was endothermic because heat energy was gained from the surroundings!

Hope this helps!! x
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Using the model, write the chemical formula for an ionic compound that has Mg and Cl.
viktelen [127]

Answer

Mg2Cl2

Mg + mg = mg2

cl + cl = cl2

Mg2 + cl2 =mg2cl2

3 0
2 years ago
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Do scientists worldwide use the same units of measurements?
AfilCa [17]
Scientist typically use the international system of measurements, or the metric system. If you mean English as in England, then yes.<span> The United States' system of measurement is not usually used by scientists.</span>
7 0
3 years ago
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rank the four gases (air, exhaled air, gas produced from the decomposition of H2O2, gas from decomposition of NaHCO3, in order o
SVEN [57.7K]

Answer: H₂O₂ (94%) > Air (23%) > Exhaled air (13%) > NaHCO₃ (0%)


Initial important note:


Although NaHCO₃ contents oxygen atoms, and you can calculate its compositoin, the resulting gas does not containg pure oxygen gas (O₂). For the comparisson it is not useful to calculate the content of oxygent atoms, but the concentration of O₂ gas. As such, the gas from NaHCO₃ contains 0% of pure O₂, that is why it is ranked last.


1) Air:


Source: internet


Approximate 23%. It is variable, because air is not a pure substance but a mixture of gases, whose compositon is not unique.


2) Exhaled air:


Source: internet.


Approximate 13%. The compositon of the air changes in our lungs, due to the respiration process: we inhale fresh air with around 23% of oxygen, part of this oxygen pass to the cells (lungs - blood - heart - cells) and then it is exhaled with a lower content of air and a greater content of CO₂


3) Air from the decomposition of H₂O₂.


In this case we can do a chemical calculation, since we can state the chemical equation of the reaction:


i) Chemical Equation:


H₂O₂ (g) → H₂ (g) + O₂ (g)


ii) mole ratio of the products 1 mol H₂ : 1 mol O₂


iii) convert moles into mass (grams)


1 mol H₂ × 2 × 1.008 g/mol = 2.016 g


1 mol O₂ × 2 × 15.999 g/mol = 31.998 g


Composition, % = [31.998 g / (2.016 g + 31.998 g) ] × 100 ≈ 94%



4) Air from the decomposition of NaHCO₃:


i) chemical equation:


2 NaHCO₃(s) → Na₂CO₃(s) + CO₂(g) + H₂O(g)


ii) mole ratio: take into account only the gases in the products:


1 mol CO₂ (g) : 1 mol H₂O


iii) mass in grams


CO₂: molar mass ia approximately 44.01 g/mol


H₂O: molar mass is approximately 18.02 g/mol


iii) Those gases although have oxygen atoms, do not hae free oxygen gas, which is what we are compariing. That means, that from the decomposition of NaHCO₃ you get 0% oxygen gas.


5) The result is:


H₂O₂ (94%) > Air (23%) > Exhaled air (13%) > NaHCO₃ (0%)

7 0
3 years ago
Read 2 more answers
Can somebody help and answer which ones are connected to each other. Correctly!
igor_vitrenko [27]

nuclear power--used to turn turbines...

fossil fuels--burned to provide energy that is....

renewable energy--energy that with come back after use

outlet--a device....

steam--nuclear reactors....

I'm not sure but I tried lol,lemme know if I'm wrong :D

3 0
3 years ago
What is the orbital or electronic geometry of a molecule with 0 nonbonding electron pairs and 2 bonding electron pairs?
disa [49]
Linear is the answer
3 0
3 years ago
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