Which statement is a disadvantage of using biofuels instead of fossil fuels?
Correct Answer: \( \boxed{\mathrm{A}} \)
A disadvantage of biofuels is that crops used to produce them require agricultural land. This land could otherwise be used to grow food crops.
Biofuels can have lower overall \( \mathrm{CO_2} \) emissions because the plants used to produce them absorb \( \mathrm{CO_2} \) during photosynthesis. Crop waste can also provide a useful fuel source.
Therefore, the correct answer is (A).
Which products may form when propane undergoes incomplete combustion?
Correct Answer: \( \boxed{\mathrm{D}} \)
Incomplete combustion occurs when there is insufficient oxygen for complete conversion of carbon into \( \mathrm{CO_2} \).
Depending on the amount of oxygen available, carbon-containing products such as \( \mathrm{CO_2} \), \( \mathrm{CO} \) and solid carbon, \( \mathrm{C} \), may form.
For example, limited oxygen can result in the formation of carbon monoxide:
\( \mathrm{2C_3H_8+7O_2\rightarrow6CO+8H_2O} \)
Therefore, the products that may form are \( \mathrm{CO_2} \), \( \mathrm{CO} \) and \( \mathrm{C} \), so the correct answer is (D).
What is the sum of the coefficients when \(1\,\mathrm{mol}\) of propan-1-ol, \( \mathrm{C_3H_7OH} \), undergoes complete combustion?
\( \mathrm{\_\_C_3H_7OH(l)+\_\_O_2(g)\rightarrow\_\_CO_2(g)+\_\_H_2O(l)} \)
Correct Answer: \( \boxed{\mathrm{C}} \)
The balanced equation for the complete combustion of propan-1-ol is:
\( \mathrm{C_3H_7OH+\dfrac{9}{2}O_2\rightarrow3CO_2+4H_2O} \)
The coefficients are \(1\), \( \dfrac{9}{2} \), \(3\) and \(4\).
Sum of coefficients:
\(1+\dfrac{9}{2}+3+4=12.5\)
Therefore, the correct answer is (C).
