PlEASE HELP! 40! A radioactive form of sodium pertechnetate is used as a brain-scanning agent in medicine. Quantitative analysis of a sample with a mass of 0.8961 g found 0.1114 g of sodium and 0.4749 g of technetium. The remainder was oxygen. Determine the empirical formula.

apples

Explanation:

moles Na = 0.1114 g / 22.9898 g/mol=0.004846

moles Tc = 0.4562g /98.9063 g/mol=0.004612

mass O = 0.8961 - ( 0.1114 + 0.4562)=03285 g

moles O = 0.3285 g/ 15.999 g/mol=0.02053

divide by the smallest

0.02053/ 0.004612 =4.45 => O

0.004846/ 0.004612 = 1.0 => Tc

to get whole numbers multiply by 2

Na2Tc2O 9

Explanation:

Hope it right hope it helps

n2(g) + 3h2-> 2nh3(g)   this is the balanced equation

note the mole ratio between n2, h2 and nh3.   it is 1 : 3 : 2   this will be important.

moles n2 present = 28.0 g n2 x 1 mole n2/28 g = 1 mole n2 present

moles h2 present = 25.0 g h2 x 1 mole h2/2 g = 12.5 moles h2 present

based on mole ratio, n2 is limiting in this situation because there is more than enough h2 but not enough n2.

moles nh3 that can be produced = 1 mole n2 x 2 moles nh3/mole n2 = 2 moles nh3 can be produced

grams of nh3 that can be produced = 2 moles nh3 x 17 g/mole = 34 grams of nh3 can be produced

note:   the key to this problem is recognizing that n2 is limiting, and therefore limits how much nh3 can be produced.

a gas, having a molecular weight of 13 kg/kmol and a kinematic viscosity of 0.25 cm2/s, flows through a pipe 0.25 m internal diameter and 5 km long at the rate of 0.4 m3/s and is delivered at atmospheric pressure.