A mixture of nitrogen and hydrogen was allowed to come to equilibrium at a given temperature. 3H2 + N2    2NH3 An analysis of the mixture at equilibrium revealed 2.1 mol N2, 2.8 mol H2, and 1.8 mol NH3. How many moles of H2 were present at the beginning of the reaction?

What is the name given to a substance that increases the rate of a chemical reaction but is not itself consumed?

If Linh _______  (to ask) her teacher, he’d have answered her questions.

Huy _______ (try) to get a job for six months, but is still unemployed.

I _______________ spend too much money today. I’ve only got a little left.

He _______ (work) in a bank when he _______ (meet) his wife.

Dad _______ (to arrive) safe if he drove slowly.

We _______ (drive) to the movie theater, when we _______ (hit) a deer.

When I ________________________ (walk) into the room, everyone ________________________ (work).

You _______________ tidy up now. Your room’s a mess.