Unit 7: Chemical Reactions Post Test

Select the correct answer from each drop-down menu. The chemical name for sand is silicon dioxide. The two elements found in a sample of this sand are [ ] and [ ].

• oxide

• sand

• silicon

• carbon

• oxygen

Select all the correct answers. Which of these processes are chemical reactions?

• boiling an egg

• crushing spices

• vegetables rotting

• chopping vegetables

• dew forming

Select all the correct answers. Which of these are examples of mixing and separating?

• removing seed casings from grains

• a soda bottle bubbling when it is opened

• a bright copper statue turning green from weathering

• removing salt from seawater

• water decomposing to oxygen and hydrogen

Select the correct answer from each drop-down menu. Identify the type of reaction represented by each equation. A: H₂ + Cl₂ → 2HCl

• combustion

• decomposition

• double displacement

• single displacement

• synthesis

Select the correct answer from each drop-down menu. Identify the type of reaction represented by each equation. B: CH₄ + 2O₂ → CO₂ + 2H₂O

• combustion

• decomposition

• double displacement

• single displacement

• synthesis

Type the correct answer in each box. Which chemical symbols will complete the equation for this single displacement reaction? 2NaBr + Cl₂ → 2 ___ + ___ ₂

• Na, Br

• Na, Cl

• K, Br

• Li, Cl

Select the correct answer. Based on the reactivities of the elements involved, which reaction will form products that are more stable than the reactants?

• 2AlBr₃ + 3Zn → 3ZnBr₂ + 2Al

• CaBr₂ + 2Na → 2NaBr + Ca

• MgBr₂ + H₂ → 2HBr + Mg

• BaBr₂ + Ca → CaBr₂ + Ba

• 2LiBr + Ba → BaBr₂ + 2Li

Select the correct answer. A substance is followed by the symbol (l) in a chemical equation. What does the symbol represent?

• The substance has the least molecules in the equation.

• The substance is in the liquid state.

• The substance is produced last in the reaction.

• The substance is dissolved in a liquid solution.

• The substance is lost at the end of the reaction.

This chemical equation is not balanced: AgBr(s) → Ag(s) + Br₂(g). Why isn’t it possible for the reaction to occur as indicated by the unbalanced equation?

• There are more substances on the right side of the equation than on the left side.

• There is a gas on the right side of the equation but not on the left side.

• The bromine atoms must go through a liquid state before becoming a gas.

• There is more mass represented on the right side of the equation than on the left side.

• The bromine atoms on the right side of the equation are not bonded to another element.

Select the correct answer from each drop-down menu. The chemical formula for naphthalene is C₁₀H₈. It's used to make mothballs and pesticides. In 4C₁₀H₈, the coefficient is [ ], the subscript of carbon is [ ], and the subscript of hydrogen is [ ].

• 8

• 5

• 12

• 10

• 4