How to create a particle model that would be more dense than a depicted one?

Numbers with a end value of 4 or lower are rounded up, while with an end value of 5 or higher are rounded down. true or false?

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

The activation energy for the reaction no2(g)+co2(g)⟶no(g)+co(g) is ea = 300 kj/mol and the change in enthalpy for the reaction is δh = -100 kj/mol . what is the activation energy for the reverse reaction?