What mass of water will be formed when 3g of hydrogen react with 30g of oxygen?​

 Write down the chemical equation first;

2H2 + O2 —-> 2H2O

2. Since the mass is given, use it to calculate the mole for each reactant;

mole = mass / molar mass

mole of H2 : 8/2 = 4 mole

mole of O2 : 30/16(2) = 0.9375 mole

Now, if you're not sure which reactant to use to calculate the mass of H2O using ratio since both answer are different, find the limiting reactant.

From the equation;

2 mol of H2 -> 2 mol of H2O

4 mol of H2 -> (4*2)/2 = 4 mol of H20

1 mol of O2 -> 2 mol of H2O

0.9375 mol of O2 -> (0.9375*2)/1 = 1.875 mol of H2O

Let's take a look at both numbers. Since H2 produces more water than O2, O2 will be the limiting reactant as it has the least mole of H2O. So now we are going to use O2 as our limiting reactant. Use the formula to calculate mass of water using mole.

mass of H2O : 1.875*(16+2) = 33.75 g

Thats it. Correct me if im wrong

Explanation: