Answer:
9
Explanation:
Protons,neutrons,electrons
6.9 (two sig figs)
2.375 + 4.5 = 6.875 = 6.9
When adding or subtracting, sig figs are determined by the least number of digits past the decimal point.
134.4 g of Mg
reaction:
2Mg + O2 ➡️ 2MgO
1) find the mol of MgO
mol = mass / molar mass
mass = 224 g
molar mass = 24+16 = 40
mol = 224 / 40
= 5.6 moles
2 mol = 5.6 moles
2) find the mass of Mg
mass = mol × molar mass
mol = 5.6
molar mass = 24
mass = 5.6 × 24
= 134.4 g