1. A sample of bromine contained the two isotopes in the following proportions: bromine-79 = 50.7% and bromine-81 = 49.3%. Calculate the relative atomic mass of bromine

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2. How many protons in a phosphorus atom?

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3. How many electrons in a magnesium atom?

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4. An oxide of nitrogen contains 26% nitrogen and 74% oxygen and has a relative molecular mass of 108. Find the empirical and molecular formulae for the oxide.

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5. State the steps for calculating empirical formula

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6. What is meant by the term molecular formula?

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7. To determine the formula of a metal oxide by combustion, magnesium is heated in a crucible. Why is the crucible is cooled, weighed, reheated, cooled, re-weighed, and so on?

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8. Calculate the relative formula mass(Mr) of propane (C₃H₈)

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9. What are the three subatomic particles?

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