Work the following calculations:
a) how many moles are in 23 grams of oxygen (z=8)?
b) what is the mass of 2.5 moles of nitrogen (z=7)?

How would the number of moles (n) of o2 change if the atmospheric pressure doubled but all other variables stayed the same

How many grams of mgbr2 are needed to produce 75g or metal?

Why is any chemical reaction always balanced? give reasons and explain the easiest way to solve the balancing problems in chemical equations with stoichiometric coefficients upto 20 as hit and trial doesn't always work. give full reasoning