Explain, i don't understand.

7. for the combustion of ethyl alcohol as described in the above equation, which of the following is true?

8. the total volume of hydrogen gas is needed to fill the hindenburg was 2.00 × 10^8 at 1.00 atm and 25.1°c. how much energy was evolved when it burned?

7. A) I, II ; 8. D) 2.34e9 kJ

Step-by-step explanation:

7. Combustion of ethanol

I. The negative sign for ΔH shows that the reaction is exothermic.

II. The enthalpy change would be different if gaseous water were produced.

That's because it takes energy to convert liquid water to gaseous water, and this energy is included in the value of ΔH.

III. The reaction is a redox reaction, because

IV. The products of the reaction occupy a smaller volume than the reactants, because 3 mol of gaseous reactant are forming 2 mol of gaseous product.

Therefore, only I and II are correct.

7. Hindenburg

Data:

  V = 2.00 × 10⁸ L

  p = 1.00 atm

  T = 25.1 °C

ΔH = -286 kJ·mol⁻¹

Calculations:

(a) Convert temperature to kelvins

T = (25.1 + 273.15) K = 298.25 K

(b) Moles of hydrogen

Use the Ideal Gas Law:

pV = nRT

n = (pV)/(RT)

n = (1.00 × 2.00 × 10⁸)/(0.082 06 × 298.25) = 8.172 × 10⁶ mol

(c) Heat evolved

q = nΔH = 8.172 × 10⁶ × (-286) = -2.34 × 10⁹ kJ

The hydrogen in the Hindenburg released 2.34e9 kJ .

c. because step up transformer steps up the input voltage i.e increases the input voltage  

the number of turns are greater on the secondary side of step up transformer  

transformer does not handle dc current

the volume increases