Answer:
A Type of Drink
Explanation:
A controlled variable remains constant throughout the experiment.
In such experiment, you'd test the volume of one single caffeinated drink. You'd have to use the same type of drink every trial.
Ammonia undergoes combustion with oxygen to produce nitric oxide and water. The volume of the oxygen required to react with 720 ml of ammonia is 900 ml.
<h3>What is volume?</h3>
Volume is the area occupied by the substance and is the ratio of the mass to the density.
At STP, 1 mole of gas occupies 22.4 L of volume
Given,
Volume of ammonia reacted = 0.720 L
The combustion reaction is shown as,

From the stoichiometry of the reaction, it can be said that,
L of ammonia reacts with
L of oxygen gas.
So, 0.720 L of ammonia will react with:

Therefore, the volume of oxygen required is 900 mL.
Learn more about volume here:
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<span>Ammonia (NH3) is the combination of Nitrogen and Hydrogen
elements.
=> N2 + 3H2 => 2NH3
Ammonia is basically used as a fertilizer. It is a gas composed of nitrogen and
hydrogen. It is colorless with strong odor. Here are some other uses of Ammonia
aside from fertilizer:
=> used by manufacturer to produce synthetic fiber
=> Used in metallurgical process
Ammonia can be decomposed easily and it produce hydrogen that is very
convenient in welding.
Ammonia’s boiling point is -28.03 F and freezing point is -107.8F.
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