Why are 3 ammonium groups needed for every 1 nitride ion?

If 15 drops of ethanol from a medicine dropper weigh 0.60g, how many drops does it takes from a dropper to dispense 1.0ml of ethanol? density of ethanol is ethanol is 0.80g/ml.

What is the magnitude of the force of gravity between to 1000 kg cars which are separated by distance of 25. 0 km on an interstate highway? the force between the two cars will be what

Why is it important for scientists to replicate each other’s experiments? to determine if important scientific results are repeatable to the research of other scientists to determine if slight alterations in the experiment can affect the result to further their own research