Atomic mass Na = 22.99 u.m.a
22.99 g ------------------ 6.02x10²³ atoms
175 g -------------------- ?? atoms
175 x (6.02x10²³) / 22.99 => 4.58x10²⁴ atoms
hope this helps!
The units of ppm means parts per million. Also, It is equivalent to milligrams per liter. It is one way of expressing concentration of a substance. It u<span>sually used to describe the concentration of something in water or soil. We calculate the mass of CaCO3 as follows:
Mass = 75 mg/L (.050 L) = <span>3.75 mg CaCO3</span></span>
1 CH4 (g) + 2 O2 (g) -----> CO2 (g) + 2H2O(l) ΔH= - 890 kJ
1 mol 2 mol
1) If ΔH has minus, it means "release". We need only "release" choices.<span>
2) From reaction
1 mol </span>CH4 (g) "releases" ΔH= - 890 kJ - We do not have this choice.
2 mol O2 (g) "release" ΔH= - 890 kJ, so
1 mol O2 (g) "release" ΔH= - 445 kJ
Correct answer is B.
