Firstly the limiting reactant should be identified. Limiting reactant is the reactant that is in limited supply, the amount of product formed depends on the moles present of the limiting reactant.
the stoichiometry of x to y = 1:2
1 mole of x reacts with 2 moles of y
if x is the limiting reactant, there are 3 moles of x, then 6 moles of y should react, however there are only 4 moles of y. Therefore y is the limiting reactant and x is in excess.
4 moles of y reacts with 2 moles of x
since there are 3 moles of x initially and only 2 moles are used up, excess amount of x is 1 mol thats in excess.
False Alkaline earth metals is group 2
Percent error (%)= 
Accepted value is true value.
Measured values is calculated value.
In the question given Accepted value (true value) = 63.2 cm
Given Measured(calculated values) = 63.1 cm , 63.0 cm , 63.7 cm
1) Percent error (%) for first measurement.
Accepted value (true value) = 63.2 cm, Measured(calculated values) = 63.1 cm
Percent error (%)=
Percent error = 0.158 %
2) Percent error (%) for second measurement.
Accepted value (true value) = 63.2 cm, Measured(calculated values) = 63.0 cm
Percent error (%)=
Percent error = 0.316 %
3) Percent error (%) for third measurement.
Accepted value (true value) = 63.2 cm, Measured(calculated values) = 63.7 cm
Percent error (%)=
Percent error = 0.791 %
Percent error for each measurement is :
63.1 cm = 0.158%
63.0 cm = 0.316%
63.7 cm = 0.791%
The answer is: the mass of oxygen is 16.95 grams.
The overall balanced photosynthesis reaction:
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂.
m(C₆H₁₂O₆) = 15.90 g; mass of glucose.
n(C₆H₁₂O₆) = m(C₆H₁₂O₆) ÷ M(C₆H₁₂O₆).
n(C₆H₁₂O₆) = 15.9 g ÷ 180.18 g/mol.
n(C₆H₁₂O₆) = 0.088 mol; amount of glucose.
From chemical reaction: n(C₆H₁₂O₆) : n(O₂) = 1 : 6.
n(O₂) = 6 · 0.088 mol.
n(O₂) = 0.53 mol; amount of oxygen.
m(O₂) = 0.53 mol · 32.00 g/mol.
m(O₂) = 16.95 g; mass of oxygen.
