Cuestionario Tema 7. Chemical reactions.

Choose the INCORRECT answer. "Some of the most common signs that tell us that a chemical reaction has occurred are":

• Change of colour

• Production of gas

• Change of mass

• Absortion or release of heat

The substances that we mix to produce a chemical

reaction are called...

• Reactants

• Products

• Compounds

• Matters

In a chemical reaction:

• The atoms of the reactants transform into different ones

  to make products. All the atoms change.

• The atoms of the reactants are arranged in a

  different way to make the products. Atoms are the same but their order in molecules change.

• The atoms of the reactants disappear

In all chemical reactions:

• The total mass of the reactants is always greater than the

  total mass of the products.

• The total mass of the reactants is always less than the

  total mass of the products

• The total mass of the reactants equals the total mass

  of the products

If 120 g of substance A reacts completely with 36 g of

substance B, then 40 g of substance A will react with:

• 15 g of substance B

• 12 g of substance B

• 24 g of substance B

• 13 g of substance B

The decomposition of magnesium oxide (MgO) produces

magnesium and molecular oxygen (O₂). The corresponding

reactions is:

• 2 MgO -> 2 Mg + O₂

• MgO -> Mg + O

• Mg + O₂ --> MgO

• 4 Mg -> 2O₂

The correctly balanced chemical equation for

C₃H₈ +O₂ --> CO₂ + H₂O

is

• C₃H₈ + 2 O₂ --> CO₂ + 4 H₂O

• 2 C₃H₈ +10 O₂ --> 6 CO₂ + 8 H₂O

• 2 C₃H₈ + 10 O₂ --> 5 CO₂ + 7 H₂O

• 4 C₃H₈ +5 O₂ --> 4 CO₂ + 6 H₂O

Choose the correct reactant to complete the balanced

chemical equation:

…. + O2 -> 2 CuO

• 2 Cu

• Cu

• 2 Cl

• 4 Cu

In the next balanced reaction:

H₂ + Cl₂ -> 2 HCl

Choose the picture with the correct answer for the products:

• 
• 
• 
• 

Let's balance the next equation:

N₂ + H₂ → NH₃

• 5 N₂ + 6 H₂ → 10 NH₃

• N₂ + 3 H₂ → 2 NH₃

• 8 N₂ + 4 H₂ → 6 NH₃

• 2 N₂ + 4 H₂ → 4 NH₃