Alkanes are hydrocarbons with the general formula Cn H2n-+2 The combustion of an

Question

Alkanes are hydrocarbons with the general formula Cn H2n-+2 The combustion of an alkane may be represented by the unbalanced general equation: CnH2n+2 + O2-+ CO2 + H2O The molar heat of combustion of a hydrocarbon is the quantity of energy released when one mole of the hydrocarbon i converted completely to carbon dioxide, CO2, and water vapor, H20 The molar heats of combustion for propane, CsHs, and pentane, CsH12 are-2100 kJ/mol and-3510 kJ/mol, respectively Which of the following is the MOST likely explanation for the difference between these two values? Elimination Tool Pentane is a larger, more polarizable molecule, so more energy is required to bring about combustion. More bond breaking and forming occurs in the combustion of pentane than in the combustion of propane. The quantity of energy released is a function of a compound's molar mass. Since pentane has the greater molar mass, its combustion produces more energy. Pentane is a liquid under normal conditions, while propane is a gas. The heat of combustion for pentane is greater because it must first be converted to the gas state before it can undergo combustion. D

Explanation / Answer

Solution:-

1) The correct answer is "B". More bond breaking and forming occurs in the combustion of pentane than propane.

pentane has five carbon but propane has only three carbon so more the number of carbon larger the heat of combustion due to more bond breaking and forming.

2) The correct answer is "C". That is precipitation reaction.

in this reaction at reactant side both the compounds are soluble but in the product, copper hydroxide precipitates out hence precipitation is the best option.

3) The correct answer is "A". 3.3 because least hydroxide ion means higher the H+ and stronger the acid. for stronger acid ka value is very high, and pKa is the negative log of Ka means lower the pKa stronger the acid.

4) The correct answer is "c". Analytical balance, flask, and burette only because there is an indicator( Thymol blue so no need of pH meter and also we have to add approx 30 mL not exactly 30 mL so the graduated cylinder is also not required.

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