What mass of the original (25.00% by mass) solution contains 0.500 mol NaOH?

In the reaction between a crushed antacid tablet and vinegar what gas is emitted

Mike and mitchell decide to have a foot race. they mark off a stretch of 100 yards, and recruit cindy to work the stopwatch. after running the race and looking at the results, cindy declared that mitchell was the fastest. so how did the boys times compare?

Is a pencil falling to the floor anon contact force, a force, or a contact force