Reversible reactions and dynamic equilibrium

Answer Key - Grade 10 Science Worksheet

Circle the best answer, or write your answer on the line.

1. 1.

   In N₂O₄ ⇌ 2 NO₂, a sealed flask starts with 1 mol of N₂O₄ and holds 0.4 mol of NO₂ at equilibrium. How many moles of N₂O₄ remain, Ari?

   0.8 mol
2. 2.

   In N₂O₄ ⇌ 2 NO₂, a sealed flask starts with 0.5 mol of N₂O₄ and holds 0.3 mol of NO₂ at equilibrium. How many moles of N₂O₄ remain, Bo?

   0.35 mol
3. 3.

   Why is equilibrium called dynamic, Jun?

   • The amounts swing up and down
   • The products keep growing
   • Both reactions keep running
4. 4.

   Colorless N₂O₄ ⇌ brown 2 NO₂ reaches equilibrium. What happens to the color, Kira?

   • It holds a steady shade
   • It fades to colorless
   • It keeps getting darker
5. 5.

   Two people juggle clubs back and forth at the same rate. Why does each keep the same number of clubs, Luz?

   • One person ends up with the clubs
   • The jugglers have stopped throwing
   • Clubs go each way at equal rates

6. Read this first

   Amounts for N₂O₄ ⇌ 2 NO₂ in a sealed flask (example data)

   time (s)	N₂O₄ (mol/L)	NO₂ (mol/L)
   0	0.1	0
   20	0.07	0.06
   40	0.055	0.09
   60	0.05	0.1
   80	0.05	0.1

7. 6.

   Using the table, by when has equilibrium been reached, Milo?

   • By 60 s
   • At 20 s
   • At 0 s
8. 7.

   Using the table, are the amounts equal at equilibrium, Noah?

   • Yes: both are 0.050
   • Yes: both are 0.100
   • No: they're 0.050 and 0.100
9. 8.

   Using the table, why does NO₂ rise by twice as much as N₂O₄ falls, Pia?

   • Each N₂O₄ makes 2 NO₂
   • N₂O₄ has 2 NO₂ inside its bonds
   • NO₂ is twice as heavy
10. 9.

    The forward and reverse rates are both 4.5. What happens to the amounts, Ren?

    • Products pile up
    • Reactants pile up
    • They stay the same
11. 10.

    A sealed flask starts with pure N₂O₄. Which rate is zero at the very start, Zee?

    • The forward rate
    • Neither rate
    • The reverse rate