Answer: 3.024 g grams of hydrogen are needed to convert 76 grams of chromium(III) oxide, 
Explanation:
The reaction equation for given reaction is as follows.

Here, 1 mole of
reacts with 3 moles of
.
As mass of chromium (III) oxide is given as 76 g and molar mass of chromium (III) oxide
is 152 g/mol.
Number of moles is the mass of substance divided by its molar mass. So, moles of
is calculated as follows.

Now, moles of
.given by 0.5 mol of
is calculated as follows.

As molar mass of
is 2.016 g/mol. Therefore, mass of
is calculated as follows.

Thus, we can conclude that 3.024 g grams of hydrogen are needed to convert 76 grams of chromium(III) oxide,
.
Then we would not have oxygen because plants give oxygen in order to breathe
The balanced equation for the above reaction is;
2K + Cl₂ ---> 2KCl
Stoichiomtery of K to KCl is 2:2
Potassium is the limiting reactant which is fully consumed in the reaction. The amount of product formed depends on amount of limits reactant present.
Number of moles of K reacted - 6.75 g/ 39 g/mol = 0.17 mol
Therefore number of KCl moles formed - 0.17 mol
Mass of KCl formed - 0.17 mol x 74.5 g/mol = 12.67 g
Start by converting mg to g. There is .001g in every miligram, so there is 0.4g in this sample.
Then find the molar mass of ibuprofen (C13H18O2) which is 206.3g/mol
Then divide grams by the molar mass to get moles of C13H18O2: (0.4g)/(206.3g/mol) = 1.94x10^-3mol C13H18O2
Then multiply moles by Avogadro's number to get molecules: (1.94x10^-3mol)/(6.02x10^23) = 1.17x10^21 molecules of ibuprofen (C13H18O2)