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. Work out the empirical formula of an oxide of chlorine contains 7.1 g of chlorine and 1.6 g of oxygen.

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3. What is meant by the term empirical formula?

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4. How many protons in a helium atom?

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

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6. A sample of carbon contained 98.90% carbon-12 and 1.10% carbon-13. Calculate the relative atomic mass of carbon

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7. Which particle(s) in an atom has a positive charge?

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8. How many electrons in an argon atom?

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9. To determine the formula of a metal oxide by combustion, magnesium is heated in a crucible. Why is a lid used?

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