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 correct answer to your question is noble gases are stable <span>due to having the maximum number of valence electrons their outer shell can hold. Meaning their outer shells are stable.
Hope this helps let me know!</span>
Answer:
B
Explanation:
The average kinetic energy of the Substance changes.
The chemical formula C₂H₆O, which is designated as option D, is equivalent to this structural formula.
<h3><u>What is a Chemical Formula ?</u></h3>
Chemical element symbols, numbers, and occasionally additional symbols like parentheses, dashes, brackets, commas, and plus (+) and minus () signs are used in a chemical formula to represent information about the chemical proportions of the atoms that make up a certain chemical compound or molecule.
- An empirical formula represents by symbols, such as Na for sodium and Cl for chlorine, with subscripts that show the relative number of atoms in each.
- The composition of any member of an entire class of compounds can be represented by a general formula, a sort of empirical formula.
To know more about Chemical formulas, refer to:
brainly.com/question/26388921
The answer is 300
3 * 100
3 * 10 * 10
30 * 10
300
Hope this helps. If it did, consider making it Brainliest!