Methanol, CH3OH, is used as race car fuel.

How many kilojoules a...

Question

Methanol, CH3OH, is used as race car fuel.

How many kilojoules are released by burning 50.0 g of methanol?

Accepted Answer

Welcome back everyone. A sideline C two H two is a gas used for welding. The combustion of a sideline releases 1301.1 kg jules Permal calculate the energy and kill a jules released and burning 65 g of a sideline. So the keyword burning 65 g of a sideline tells us our value for Q, which we should recall represents our variable for heat. So recall that heat is another form of energy and we're going to be calculating our value for Q and what that represents in our combustion of a seedling. So to calculate Q, we would begin with our mass of our sample being 65. g of a seedling C two H two. And beginning with this mass, we're going to want to cancel out our unit of grams because we're going to recall our molar mass of a seedling from our periodic table which tells us that we have in the denominator 26 point oh four g of a seedling C two H two and this is per mole. So per one mole of seedling in the numerator. So canceling out our unit of gramps, we're left with moles of a seedling. And let's recall that our unit for heat is going to be in killing jewels as the prompt states us to give. So note that were given the amount of energy released as 1301.1 kg per mole. Now recognize that the 1301.1 kg per mole describes delta H which we recall represents our entropy change or heat content of our system from its initial state versus its final state. And we're told that this amount of entropy is released. So we should recall that this means that we have negative 1301.1 kill a jules per mole again negative because we're told that heat is released. And so whenever we have an entropy change, that is negative, recalled that this means that our reaction is exo thermic. So we can cancel our unit of moles by multiplying by this entropy as a conversion factor where we would have in our denominator, one mole of acetylene C two H two with an equivalence of negative 1301. kg jewels of heat exchange in our reaction. And using this conversion factor will now be able to cancel our units of moles of a seedling leaving us with killer joules of energy as our final unit. So in our calculators, we're going to simplify and come up with a result where Q is equal to negative 3247. kg joules of heat or energy that is released when we burn our 65 g of a seedling. So what's highlighted and yellow, negative 3247.75 kg joules will be our final answer. But let's go ahead and round this to our minimum number of sig figs as three sig figs based on our least precise measurement being our massive seedling 65 g, which also had three sig figs. And this would give us an answer of negative 3250 kg jewels and so negative 3250 killed jules would be our final answer corresponding to choice d in the multiple choice to complete this example. I hope this made sense and let us know if you have any questions.

Methanol, CH3OH, is used as race car fuel. How many kilojoules are released by burning 50.0 g of methanol?

주요 개념

Combustion Reaction

Molar Mass

Enthalpy of Combustion

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