Question

In photosynthesis, $6$ molecules of carbon dioxide combine with an equal number of water molecules through a complex series of reactions to give a molecule of glucose with the molecular formula${\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6$. How many grams of water would be required to produce $18\mathrm{g}$ glucose? Compute the volume of water so consumed assuming the density of water to be $1\mathrm{g}{\mathrm{cm}}^{-3}$

Answer 1

Photosynthesis:

1. The process through which green plants and other organisms use sunlight to synthesize nutrition from carbon dioxide and water is called photosynthesis.
2. It occurs in the chloroplast of leaves in presence of sunlight. It uses carbon dioxide and water and releases oxygen
3. The reaction during photosynthesis is given by $6O_2+6H_{2}O\underset{sunlight}{\overset{chlorophyll}{\to }}{C}_6{H}_{12}{O}_6+6O_2$

Step 1: Given data

Molecules of carbon dioxide$=6$

Molecules of water$=$ molecules of carbon dioxide

Mass of glucose$=18\mathrm{g}$

Density of water$=1\mathrm{g}$

Step 2: Applying the formula

$6O_2+6H_{2}O\underset{sunlight}{\overset{chlorophyll}{\to }}{C}_6{H}_{12}{O}_6+6O_2$

From the balanced reaction, we can see that $1$ mole of glucose needs $6$ moles of water

So, the amount of water required by $180\mathrm{g}$ of glucose needs i.e. one mole of glucose$=6\times 18\mathrm{g}\Rightarrow 108\mathrm{g}$

Therefore, the amount of water required by $1\mathrm{g}$ of glucose=108/180g$=\frac{108\mathrm{g}}{180\mathrm{g}}\Rightarrow 0.6\mathrm{g}$

Amount of water required by $18\mathrm{g}$ of glucose$=0.6\mathrm{g}\times 18\mathrm{g}\Rightarrow 10.8\mathrm{g}$

Now, volume of water used=Mass/ density=10.8g/1=$=\frac{\mathrm{Mass}}{\mathrm{density}}\Rightarrow \frac{10.8\mathrm{g}}{1\mathrm{g}{\mathrm{cm}}^{-3}}$or $10.8{\mathrm{cm}}^3$

Therefore, the volume of water used is $10.8{\mathrm{cm}}^3$.