Unit 3 Lesson 8 - Energy in Chemical Reactions

Which is true about this reaction?

C2H4O2 + NaHCO3 → NaC2H3O2 + H2O +CO2 + energy

• Acetic acid (C2H4O2) reacts with sodium bicarbonate (NaHCO3) to form sodium hydroxide (NaOH), water (H2O), and carbon dioxide (CO2)
• Acetic acid (C2H4O2) reacts with sodium bicarbonate (NaHCO3) to form sodium chloride (NaCl), water (H2O), and carbon dioxide (CO2)
• Acetic acid (C2H4O2) reacts with sodium bicarbonate (NaHCO3) to form acetic anhydride (C4H6O3), water (H2O), and carbon monoxide (CO)
• Acetic acid (C2H4O2) reacts with sodium bicarbonate (NaHCO3) to form sodium acetate (NaC2H3O2), water (H2O), carbon dioxide (CO2), and energy.

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Is this reaction endo or exothermic?

C2H4O2 + NaHCO3 → NaC2H3O2 + H2O +CO2 + energy

• Exothermic

• Endothermic

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Is this reaction endo or exothermic?

MgSO4 (s) + H2O (l) + energy → Mg^2+ (aq) + SO4^2- (aq)

• Endothermic

• Exothermic

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What is true about this reaction?

MgSO4 (s) + H2O (l) → Mg^2+ (aq) + SO4^2- (aq)

• The reaction shows the formation of MgSO4 from Mg^2+ and SO4^2- ions in aqueous solution.
• The reaction shows the combination of MgSO4 and Mg^2+ ions in aqueous solution.
• The reaction shows the release of MgSO4 from Mg^2+ and SO4^2- ions in aqueous solution.
• The reaction shows the dissociation of MgSO4 into Mg^2+ and SO4^2- ions in aqueous solution.

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In endothermic reactions energy moves into the system.

• True

• False

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Which is true about an exothermic reaction?

• Always involves a solid and a liquid.

• Causes a cooling effect in the surrounding environment.

• Is a reaction in which the atoms in a substance expand or explode.

• Releases more energy into the surroundings than it absorbs.

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The root "therm" means _______?

• Atom

• Heat

• Cooling

• Reaction

A system is?

• A device that scientists use to create a chemical reaction.

• The environment in which a chemical reaction takes place.

• The substances that are involved in the chemical reaction.

• A chemical reaction that does not release or absorb any energy.

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Which of these is NOT part of the system in a chemical reaction of a match being lit?

• The wooden splint.

• The oxygen in the air.

• The hand lighting the match.

• The substances in the match head.

How does iron powder function as a hand warmer?

• Iron powder mixed with water causes an exothermic reaction.

• Iron powder has a low melting point, so it easily produces heat.

• The iron and the oxygen in the air mix, causing an exothermic reaction.

• The heat from rubbing your hand causes an exothermic reaction with the iron.

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