Chemistry questions. Please helppp.?

1. in the US-- we use STP, after teaching chem for 40 years, I've never heard of NTP. as the other answerer stated you can use the ideal gas law in one of its several forms ... but 1 mole of a gas at STP occupies 22.4 L.
--- easier to do a proportion --- (sorry, your teacher probably wants unit cancellation)
2g / 1L = x / 22.4L <<< proportion
>>> unit cancellation ... 22.4L X (2g / 1L) = 44.8 g << molar mass

2. 100 mL 0.5 M Naoh is mixed with 50 mL 0.2 M Naoh solution and the mixture is diluted to 500 mL. Find the molarity of the mixture.
M X mL = milimoles
mmole NaOH = 100(0.5) + 50(0.2) = 60mmole
molarity mole/ liter AND mmole/mL
total volume = 500mL << it is diluted to this volume
M = 60mmole / 500 = 0.12 M <<< answer

1. Begin with the ideal gas law:
PV = n RT
The number of moles, n, can be replaced by mass/MW. Making that substitution and rearranging gives:
MW = mass (RT)/PV
Substitute your values into the equation and calculate the molar mass.

2. Calculate moles NaOH in each solution. Add them together and divide by the final volume, in L:
0.100 L X 0.5 mol/L = 0.05 mol NaOH
0.050 L X 0.2 mol/L = 0.01 mol NaOH
Total moles NaOH = 0.060 moles
Final Molarity = 0.060 moles / 0.5 L = 0.12 M NaOH