Lesson Worksheet: Conservation of Elements Chemistry

In this worksheet, we will practice describing the conservation of elements during chemical reactions.


Fill in the blank: A chemical compound is made up of .

  • Afewer than three elements
  • Bonly two atoms
  • Cmore than two atoms
  • Da single element only
  • Etwo or more different elements


Which of the following chemical entities is a compound?

  • ACu
  • BNaCl
  • CH2
  • DO3
  • EN2


In which of the following chemical reactions is the concept of conservation of elements not obeyed?

  • AFeCl+ZnFeCl+Cu22
  • BCaO+COCaCO23
  • CNH+HClNHCl34
  • DMg+CuSOMgSO+Cu44
  • EZnCOZnO+CO32


Which of the following statements best describes the conservation of elements during a chemical reaction?

  • ANo element can appear or disappear during a chemical reaction.
  • BElements can disappear but not appear during a chemical reaction.
  • CElements can appear but not disappear during a chemical reaction.
  • DElements can appear or disappear during a chemical reaction.


By using the concept of conservation of elements, identify the element missing in the following chemical equation: Mg+HSOSO+H2442

  • AH
  • BO
  • CNa
  • DMg
  • ES


Nitrogen and oxygen in the air can combine in a series of reactions to produce a variety of nitrogen oxides. Using the concept of conservation of elements, determine which of the following could not be a possible product of these reactions?

  • AHNO3
  • BNO25
  • CNO2
  • DNO
  • ENO23


Students combine concentrated nitric acid with copper metal and observe a vigorous chemical reaction. They notice a color change and effervescence as copper metal transforms into a copper nitrate product. What is the name of the gas this chemical reaction process produces?

  • ANitrogen dioxide
  • BElemental oxygen
  • CElemental nitrogen
  • DNitrous acid
  • ENitric oxide


A pale blue precipitate forms when copper(II) sulfate reacts with sodium hydroxide. What is the identity of the precipitate?

  • ASodium copper sulfate
  • BCopper(III) hydroxide
  • CCopper oxide
  • DSodium sulfate
  • ECopper(II) hydroxide


Magnesium reacts explosively with oxygen to form magnesium oxide according to the following equation: 2Mg+O2MgO2

Which of the following is not true of this reaction?

  • AMagnesium oxide has similar physical and chemical properties to both oxygen and magnesium.
  • BThe reactants, magnesium and oxygen, are elements.
  • CThe concept of conservation of elements is obeyed.
  • DThe product of the reaction, magnesium oxide, is a compound.
  • EThe reaction describes the formation of a new substance.


A student heats a mixture of copper(II) oxide and carbon. They produce carbon dioxide and a reddish-orange solid. What is the identity of the reddish-orange solid?

  • ACopper carbonate
  • BCopper dioxide
  • CCopper metal
  • DCopper(III) oxide
  • ECopper trioxide

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