[Yogi1]

Through a series of enzymatic steps, carbon dioxide and water produce glucose and oxygen
in the process of photosynthesis according to the equation
6CO2(g) + 6H2O(l) -> C6H12O6(s) + 6O2(g)
Given that the partial pressure of carbon dioxide in the troposphere (lower atmosphere)
is 0.26mmHg (= 0.26 Torr) and that the temperature is 25 C, calculate the volume of air
that is needed to produce 10.0 g of glucose.
Hint: The partial pressure equals the pressure we would get if carbon dioxide were alone
in the same volume.

[RandoFlyer]

For this question you can use the formula PV=nRT
You will want to solve for "V"

First things first, find out how many moles are in 10.0g of sucrose.  Use a mole ratio to then find the moles of CO2 in the reaction, this value will be your "n".  Convert your partial pressure into Pascals, this will be your "P". "T" is always in Kelvins so convert 25C into Kelvin.  "R" is the gas constant, which is approximately 8.314. 

Sub in your values and solve for V!

[Yogi1]

Tyvm for help
But should not R be 0,0821 and P in atm?

[Borek]

Value of R depends on the units, there is an extensive table with collected values in wikipedia.