Answer:
The reaction of one mole of oxygen (O2) releases 445 kJ of energy.
Explanation:
Firstly, the reaction is exothermic since the sign of enthalpy change ΔH is negative.
The balanced equation: CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(l): ΔH = −890 kJ,
Shows that 1 mole of CH₄ react with 2 moles of oxygen and releases 890 kJ.
So, every choice says that absorb is wrong (choice 1& 3).
Choice no. 4 is wrong since it says that 2 moles of methane releases 890 kJ, because only one mole release this amount of energy.
So, the right choice is The reaction of one mole of oxygen (O2) releases 445 kJ of energy.
The answer is C. Zn(s) + H2SO4(aq) ZnSO4(aq) + H2(g)
Answer: -134 kJ
Explanation:
The balanced chemical reaction is,
The expression for enthalpy change is,
![\Delta H=\sum [n\times \Delta H_f(product)]-\sum [n\times \Delta H_f(reactant)]](https://tex.z-dn.net/?f=%5CDelta%20H%3D%5Csum%20%5Bn%5Ctimes%20%5CDelta%20H_f%28product%29%5D-%5Csum%20%5Bn%5Ctimes%20%5CDelta%20H_f%28reactant%29%5D)
![\Delta H=[(n_{HNO_3}\times \Delta H_{HNO_3})+(n_{NO}\times \Delta H_{NO})]-[(n_{H_2O}\times \Delta H_{H_2O})+(n_{NO_2}\times \Delta H_{NO_2})]](https://tex.z-dn.net/?f=%5CDelta%20H%3D%5B%28n_%7BHNO_3%7D%5Ctimes%20%5CDelta%20H_%7BHNO_3%7D%29%2B%28n_%7BNO%7D%5Ctimes%20%5CDelta%20H_%7BNO%7D%29%5D-%5B%28n_%7BH_2O%7D%5Ctimes%20%5CDelta%20H_%7BH_2O%7D%29%2B%28n_%7BNO_2%7D%5Ctimes%20%5CDelta%20H_%7BNO_2%7D%29%5D)
where,
n = number of moles
Now put all the given values in this expression, we get
![\Delta H=[(2\times -207)+(1\times 90)]-[(1\times -286)+(3\times 32)]](https://tex.z-dn.net/?f=%5CDelta%20H%3D%5B%282%5Ctimes%20-207%29%2B%281%5Ctimes%2090%29%5D-%5B%281%5Ctimes%20-286%29%2B%283%5Ctimes%2032%29%5D)
Therefore, the enthalpy change for this reaction is, -134 kJ
Answer:
Chemical formula for the black iron oxide sample is FeO
Explanation:
<u>Given:</u>
Mass ratio of black iron oxide sample, Fe/O = 3.491
<u>To determine:</u>
The chemical formula
<u>Calculation:</u>
The mass ratio is Fe:O = 3.491 : 1
Mass of Fe = 3.491 g
Mass of O = 1.000 g
Atomic mass of Fe =55.85 g/mol
Atomic mass of O = 16.00 g/mol
Therefore, the molar ratio of Fe:O = 1:1
Hence, chemical formula is FeO
Correct answer choice is :
D) The pitch of the sound being heard by the person will appear to be lower than the pitch of the source.
Explanation:
The sensation of a frequency is usually related to as the pitch of a sound. A high pitch sound relates to a high-frequency sound wave and a low pitch sound relates to a low-frequency sound wave. Whereas loudness depends on the power of the wave. In overall, the pitch is the cause behind the variation in voice quality for several people. The pitch of a sound depends on the frequency while loudness of a sound depends on the amplitude of sound waves.
