Question 25 for each chemical reaction in the table below, decide whether the highlighted reactant is a brønsted-lowry acid, a brønsted-lowry base, or neither.

According to the Bronsted-Lowry definitions, an acid is any substance that donates hydrogen ions; whereas, a base is any substance that accepts hydrogen ions. 

In the first reaction, water is acting as an acid because it donates a hydrogen ions.

In the second reaction, water is acting as a base because it accepts a hydrogen ion.

In the third reaction, water is again donating a hydrogen ion so it is the acid.

In the fourth reaction, water is acting as a base by accepting the hydrogen ion from the ammonium ion.

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Mass is the amount of matter in an object.  weight is the measurement of the pull of gravity on an object.  say for example, you travel to the moon which has a different gravitational field compared to the gravitational field of earth. (gravitational fields: earth = 1, moon = 0.165)  now when you are on the moon, the pull of gravity on you is different than on the earth. and as weight is the measurement of the pull of gravity on an object, that means yes, your weight can and will change on the moon.  however, on the moon, on earth or even on jupiter, the amount of mass inside of you remains the same. meaning your physical mass remains constant.  in conclusion it is possible for your weight to change as your mass remains constant.