A student determined the mass of a substance to be 28g. If the true value is 30g, what is the percent error in the student's determination? A) -7.14%
B) -6.67%
C) 7.14%
D) 6.67%

Agas mixture with a total pressure of 745 mmhg contains each of the following gases at the indicated partial pressures: co2, 245 mmhg ; ar, 119 mmhg ; and o2, 163 mmhg . the mixture also contains helium gas. part a what is the partial pressure of the helium gas? phe p h e = nothing mmhg request answer part b what mass of helium gas is present in a 10.2-l sample of this mixture at 283 k ? m m = nothing g request answer

Acurium-245 nucleus is hit with a neutron and changes as shown by the equation. complete the equation by filling in the missing parts. 52

The molality of calcium chloride (cacl2) in an aqueous solution is 2.46 m. what is mole fraction of the solute?