Answer:
1.94
Explanation:
moles = mass/Mr so you have 3.889 moles of aluminium, but because the ratio in the equation is 2:1 you need to halve it.
D.
Blue litmus paper turns red when placed in a base.
Acid-base indicator changes color based on pH.
drop some in a solution n watch the color changes. different indicators show different colors at different pH. they usually have standard colors for comparison.
I don’t know what exactly is but see at the picture.