Glucose, also known as 'blood sugar' when measured in blood, has the formula C6H12O6.

What is the minimum amount of energy (in kJ) a plant must absorb to produce 15.0 g of glucose?

Question

Glucose, also known as 'blood sugar' when measured in blood, has the formula C6H12O6.

What is the minimum amount of energy (in kJ) a plant must absorb to produce 15.0 g of glucose?

Accepted Answer

Welcome back everyone. Sucrose C 12 H 22 0 11 is the end product of photosynthesis and is found in a lot of food plants. The complete combustion of sucrose releases 5155.7 kg per mole of energy. Calculate the amount of energy required to produce 18.0 g of sucrose. So let's begin by writing out our complete combustion of sucrose where are sucrose C 12 H 22 0 reacts with oxygen gas and recall that sucrose is a solid. So these two will react to form carbon dioxide gas as a product as well as liquid water as a product And rather not liquid water but water in vapor form based on the high temperature required for this combustion. In order for this reaction to be balanced, we're going to need to add in the falling coefficients. A 12 in front of oxygen gas, a 12 in front of carbon dioxide gas on the product side and an in front of vapor water on the product side with these coefficients added, we now have a balanced combustion equation. And we're told that for this complete combustion of sue gross. We have a release of energy being 5155.7 kg per mole of energy. And so recall that this term is describing the heat exchange of our system. And so recall that we represent that by our entropy change delta H which will say is equal to negative 5155.7 kg per mole of energy in the form of heat. Now note that we made it negative because again, the prompt says that this amount of energy is released and recall that when we have an entropy change, that is negative, this tells us that therefore, our reaction is exo thermic involving the release of heat, which is what we have shown. So next, we want to show the production of sucrose. So we're going to show the reverse process of our reaction above In which we would begin with our 11 moles of water In vapor form, reacting with our 12 moles of carbon dioxide gas which forms on our product side, our sucrose C 12 H 22 0 in solid form as well as our 12 moles of oxygen gas as a second product for this reverse product process. Sorry, we're going to flip our entropy sign so that we now have an entropy change equal to positive 5155.7 kg joules per mole. Recall that when entropy changes positive, this therefore, tells us that we have a reaction that is going to be in the reverse process, specifically endo thermic, meaning that we have energy that is absorbed and required by our system being our reaction. And what we need to focus on is figuring out how much energy in the form of heat is required to produce specifically 18 g of sucrose. So we want to recall that energy In the form of heat is represented by the variable Q. And this is what we're going to be calculating for. So beginning with our given 18.0 g of sucrose, we want to recall that our unit for heat Q Is represented in killing jewels. So we're going to need to cancel out grams by multiplying by the conversion factor utilizing our molar mass of sucrose from the periodic table which we see in the denominator is 342.30 g of sucrose where this is per mole of sucrose in the numerator. So canceling out grams of sucrose, we now have moles of sucrose, but we need killer jewels as our final unit. And this is where we're going to incorporate our given entropy change for the reverse process which shows the production of sucrose on the product side where we have for one mole of sucrose in the denominator, the release or rather not release but absorption. Since this is going to be an endo thermic process in the reverse process, the absorption of positive 5155. kg of heat that is absorbed and required by our system. And so canceling out moles of a sucrose. Sorry, we're left with killer jewels as our final unit. And in our calculators, this will yield a Q value equal to 271.115 kg joules of energy required to form our 18 g of sucrose. Now notice that are massive sucrose, 18.0 g has a total of three sig figs. So we want around our final answer to three sig figs as 271. So positive 271 kill jules of energy required. And this would be our final answer corresponding to choice c in the multiple choice to complete this example. So I hope this made sense and let us know if you have any questions.

Glucose, also known as 'blood sugar' when measured in blood, has the formula C6H12O6. What is the minimum amount of energy (in kJ) a plant must absorb to produce 15.0 g of glucose?

Verified Solution

Key Concepts

Photosynthesis

Energy Conversion

Molar Mass of Glucose