What is an advantage of having internationally agreed hazard symbols?

) 8.000 g of CaCO3 was heated strongly for about 10 minutes. 6.213 g of solid remained. Calculate the mass of carbon dioxide gas given off.

the horizontal lines on the periodic table are called

Why is iron used in the Haber process?

An atom of element X has an atomic number of 119 and a mass number of 319. How many protons does it have?

Throughout the experiment the volume of hydrogen and the volume of oxygen are measured at two-minute intervals. Describe what the results show about the volumes of hydrogen and of oxygen produced in this experiment.

Explain why relative atomic masses of some elements are whole numbers, but those of some other elements, for example chlorine, are not.

Calculate the relative formula mass of calcium carbonate, CaCO3. (relative atomic masses: C = 12, O = 16, Ca = 40)

What does the symbol Na stand for?

Is chlorine an alkali metal, alkaline Earth metal, halogen or noble gas?

Explain why the pH of a hydrochloric acid increases when pure water is added

For an atom of atomic number 137, how many electrons does it contain?

Which of the following is NOT a diatomic molecule? hydrogen, bromine, phophorous, nitrogen or