Answer:
Amount of Niobium-91 initially
= 300/91 =3.2967mol
2040 years = 3 ×680 = 3 half-lives
therefore, amount left = 0.4121mol
mass of Niobium-91 remaining = 0.4121 ×91 =37.5g
Please give brainliest
1.linear pair
2. neither
3. vertical
4. neither
5. vertical
6. neither
7. linear pair
8. neither
Their starting from up to down not side to side
You should ender 0.5 for a half note, 0.25 for a quater note, 0.125 for a eigth note, 0.0625 for a sixteenth note.
20 with a number minus what will equal 9. ^_^
