Which of the following pairs does not share the same empirical formula?

ch2o and c3h6o3
pbcl2 and pbcl4
no2 and n2o4
c3h12 and ch4

Significant figures are digits read directly from the measuring instrument plus one more digit, which is __ by the observer.

Sally is making a model of a magnesium atom with an atomic mass number of 24 for her chemistry class. she has foam balls for the protons, neutrons, and electrons. she has added 6 neutrons to her model so far. how many more neutrons does she need to add to complete her neutral atom of magnesium?

Given the following reaction: c3h8+5o2=3co2+4h20 how many grams of co2 will be produced 7 g of c3h8 and 98 g of o2