The one that is not a compound is Cl
Answer:
The correct answer is B.
Explanation:
The molecule of water has 2 atoms of hydrogen and 1 atom of oxygen.
The ratio of masses are given as:

This illustrates the law of definite proportions which is also known as law of constant compositions .
The law states that 'the elements combining to form compound always combine in a fixed ratio by their mass.'
Whereas :
Law of multiple proportion states that when two elements combine with each other to form more than one compounds , the mass of one element with respect to the fixed mass of another element are in ratio of small whole numbers.
Law of conservation of mass states that mass can neither be created nor be destroyed but it can only be transformed from one form to another form.
In a balanced chemical reaction ,total mass on the reactant side must be equal to the total mass on the product side.
Law of conservation of energy states that energy can neither be created nor be destroyed but it can only be transformed from one form to another form.
Answer:

Explanation:
The formula for efficiency is

Data:
Useful energy = 3 J
Energy input = 30 J
Calculation:

I would say you should use or test it once a week to ensure it is working properly in an active laboratory since it is a workplace with significant chemical hazards so it would give peace of mind to know on a quite regular basis that it can be relied on in case of an emergency like an eye flush for example.