By titration it is found that 38.1 ml of 0.147 m naoh(aq) is needed to neutralize 25.0 ml of hcl(aq). calculate the concentration of the hcl solution.

You must know what reaction happens during titration:

HCl + NaOH --> NaCl + H₂O

So, the ratio for HCl to NaOH is 1:1.

The solution is as follows:

Concentration of HCl = Moles HCl/L solution
Concentration = (0.147 M NaOH)(0.0381 L)(1mol HCl/1 mol NaOH)/0.025 L
Concentration = 0.224 M HCl

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.