Answer:- 448 mL of hydrogen gas are formed.
Solution:- It asks to calculate the volume of hydrogen gas formed in milliliters at STP when 0.020 moles of magnesium reacts with excess HCl acid. The balanced equation is:

There is 1:1 mol ratio between Mg and hydrogen gas. So, the moles of hydrogen gas is also equals to the moles of Mg reacted.
moles of Hydrogen gas formed = 0.020 mol
At STP, volume of 1 mol of the gas is 22.4 L. We need to calculate the volume of 0.02 moles of hydrogen gas.

= 0.448 L
They want answer in mL. So, let's convert L to mL using the conversion formula, 1L = 1000mL

= 448 mL
So, 0.020 moles of magnesium would produce 448 mL of hydrogen gas at STP on reacting with excess of HCl acid.
The total charge on an atom comes from protons and electrons.
The proton is positively charged while the electron is negatively charged. A neutral atom would have an equal number of protons and electrons.
An atom with more protons than electrons will be positively charged while those with more electrons than protons will be negatively charged.
More on the atom can be found here: brainly.com/question/1641336
The last answer
the place where the organisms live
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Explanation:
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