3. Theoretically how many grams of magnesium is required to produce to 5.0 g of Magnesium oxide?

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

answer: c. the experiment shows that the red substance experienced a chemical change.

explanation: chemical change is the change in which chemical composition of the substance changes. physical change is the change in which there is no change in chemical composition.

chemical changes are accompanied by following changes:

a) precipitate formation

b) energy is released or absorbed

c) formation of bubbles

d) change in color

as it is given that the red color has disappeared and there is production of gas, it means the red substance has undergone a chemical change.

e