Answer:
90.5mL is the volume of the gas at STP
Explanation:
It is possible to find volume of a gas when conditions of temperature and pressure change using combined gas law:

Where P is pressure, V is volume and T is absolute temperature. 1 is initial conditions and 2 final conditions.
If initial conditions are 1.08atm, 80.0mL and absolute temperature is (-12.5°C + 273.15) = 260.65K.
And STP are 1atm of pressure and 273.15K of absolute temperature. Replacing:

V₂ = <em>90.5mL is the volume of the gas at STP</em>
Answer:
3grams
Explanation:
The reaction for the production of Magnesium dioxide will be
Mg + O2 → MgO
we have 5g of MgO (molar mass 40g)
no of moles of MgO = 5/40 = 0.125
Using unitary method we have
1 mole of Mg require 1 mole of MgO
0.125 Mole of MgO = 0.125mole of Mg
n = given mass /molar mass
0.125 = mass / molar mass
mass = 0.125* 24 = 3grams
D 4 grams
i need to write a couple more character for explanation so there