How many grams of MgO are produced when 40.0 grams of O2 react completely with Mg in the following reaction 2 Mg (s) + O2 (g) –> 2 MgO (s)

An element has two naturally occurring isotopes. One isotope has a mass = 35.0 amu and makes up 24.2% of the sample, the other isotope has a mass = 37.0 amu and makes up 75.8% of the sample. What is the average atomic mass for this element?

What is the symbol of the element in Group 4A (14) in Period 2?

The Group 8A (18) elements are called the

The number of electrons in the outer energy level (ie., number of valence electrons) of a neutral atom of boron (atomic number 5) is:

The correct conversion factor to calculate the number of Liters in 5,687 ml is:

A package of hardware parts has 180 washers, 93 bolts, 44 nuts, and 19 spacers.  What percentage of the parts are spacers? 

Solve this equation:  18 + (8 x 4) x 53 – (8 – 4) + 44 =

A sack of potatoes weighs 145 lbs on earth and 11 kg on the moon.  Which of the following statements is TRUE.

The Ka of H2CO3 is 4.3 × 10-7. What is the pH of a buffer with 0.10 M H2CO3 and 0.010 M NaHCO3 (HCO3 -)?             Equation: H2CO3  +   H2O H3O+  +  HCO3 –