Today, there are about how many people living on the earth?

3.4 billion

7.5 billion

9.0 billion

6.6 billion

What is the energy required to excite one na atom (wavelength = 589 nm) ? to excite one mole of na atom?

By making several measurements with the same balance, a chemist obtained values of 5.224 g, 5.235 g, and 5.259 g for the mass of a sample. Without knowing the actual mass of the sample, we can tell that these measurements have.

In a laboratory experiment, John uses a mesh to separate soil particles from water. Which technique of separation is he using? A. chromatography B. distillation C. filtration D. fragmentation E. condensation

Isooctane has the molecular formula C8H18. What is its empirical formula

A set-back only occurs at the beginning of an exercise program cannot be overcome is normal is only the result of poor training

Which trends are observed when the elements in Period 3 on the Periodic Table are considered in order of increasing atomic number? (1) The atomic radius decreases, and the first ionization energy generally increases.

The enthalpy of formation of MX is ΔHf° = - 525 kJ/mol. The enthalpy of sublimation of M is ΔHsub = 139 kJ/mol. The ionization energy of M is IE = 437 kJ/mol. The electron affinity of X is ΔHEA = - 313 kJ/mol. (Refer to the hint).

Which group of elements could you not use in making fireworks?

A 5.0 M solution of HCL in water has a proton concentration of _M

How many moles are in 25.5 grams of Silver, Ag?