1. 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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2. 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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3. Explain why atoms are neutral

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4. What is the relative atomic mass (Aᵣ) of a helium atom?

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5. To determine the formula of a metal oxide by combustion, magnesium is heated in a crucible. Why is a lid lifted from time to time?

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6. Calculate the relative formula mass(Mr) of calcium hydroxide (Ca(OH)₂)

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7. How many electrons in the outer shell of group 4 elements?

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8. What is the empirical formula of a compound in which 0.48 g of carbon combines with 0.08 g of hydrogen and 0.64 g of oxygen?

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9. What is meant by the term empirical formula?

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