Which of the substances are elements please help

How does litmus paper indicate an acid?

Imagine that you’re getting ready to move to a new city. when people move, they are influenced by push factors and pull factors, and you have many reasons for your move. which of the following factors is an example of a pull factor? a. wanting to move because you’ve found a great new school somewhere new b. needing to move because there are not enough resources in your old hometown c. being forced to move because your old home is gone d. having to move because there are no jobs in your current hometown

If 22.5 liters of oxygen reacted with excess of hydrogen, how many liters of water vapor could be produced?