Question

According to photosynthesis equation to produce 180g glucose and 193g oxygen, plant will absorb ``X'' g of carbondioxide and ``Y'' g water and consume ``Z'' K.cal of solar energy. `X', `Y' and `Z' are respectively

• A. X - 108 g, Y - 264 g, Z - 766.2 K.cal
• B. X - 204 g, Y - 180 g, Z - 567.2 K.cal
• C. X - 264 g, Y - 108 g, Z - 677.2 K.cal
• D. X - 246 g, Y - 164 g, Z - 477.2 K.cal

Hint:

Always check if the question implies the simplified equation ($6H_2O$) or the complete physiological equation ($12H_2O$). Here, the options dictate the use of the simplified stoichiometry.

Answer 1

The Correct Option is C

Step 1: Understanding the Photosynthesis Equation:
The simplified chemical equation for photosynthesis is often written as: \[ 6CO_2 + 6H_2O \xrightarrow[\text{Chlorophyll}]{\text{Light}} C_6H_{12}O_6 + 6O_2 \] Energy values ($\Delta H$) associated with the formation of 1 mole of glucose are approximately 686 K.cal (or 677.2 K.cal as per specific textbook data used here).
Step 2: Calculating Molecular Masses:

Glucose ($C_6H_{12}O_6$): $1 \text{ mole} = 180 \text{ g}$ (Given).
Oxygen ($6O_2$): $6 \times 32 = 192 \text{ g}$ (Given approx 193 g).
Carbon Dioxide ($6CO_2$): $6 \times (12 + 2\times16) = 6 \times 44 = 264 \text{ g}$.
Water ($6H_2O$): $6 \times (2 + 16) = 6 \times 18 = 108 \text{ g}$.

Step 3: Matching Values to X, Y, Z:

X ($CO_2$ absorbed): 264 g.
Y ($H_2O$ absorbed): Based on the simplified equation stoichiometry matching X, it corresponds to 6 moles, i.e., 108 g. (Note: The complete equation $6CO_2 + 12H_2O \rightarrow C_6H_{12}O_6 + 6O_2 + 6H_2O$ involves 216g input, but the options only support the simplified 108g value).
Z (Energy): 677.2 K.cal (matches Option C).

Step 4: Final Answer:
The correct set is X = 264 g, Y = 108 g, Z = 677.2 K.cal.