Would you be nice and help me with this?

okay i was doing my homework and i got stuck in these questions, can you please help me b4 midnight, becuz this assignment is online, and i have a limited number of times to submit my answers, i have tried almost all of the questions below but did't get them right :( ?

1)Most community water supplies have 0.5 ppm of chlorine added for purification. What mass of chlorine must be added to 127.0 L of water to achieve this level?>>g

2)A 4.54 L container holds 15.4 g of oxygen at 22.55°C. What is the pressure?>>>kPa (i tried 521, 520.7, 517, 519 but none of them worked and now i only have one chance for this one)

3)A polyethylene plastic weather balloon contains 4.0 mol of helium, which is at -61°C and 1.1 103 Pa. What will be the volume of the balloon?>>>L (i tried 6.4 and 6.41 but they were wrong)

4)Suppose a certain automobile engine has a cylinder with a volume of 506.0 mL that is filled with air (21% oxygen) at a temperature of 55°C and a pressure of 101.0 kPa. What mass of octane must be injected to react with all the oxygen in the cylinder?
2 C8H18(l) + 25 O2(g) 16 CO2(g) + 18 H2O(g)

Answer:
you hsould probably do this ur self
number 1 is.635
ur really good at this!
wat gr cemistry do u take

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