Chemical Reactions

In a chemical reaction, the mass of the reactants is 13.3 grams. Which of the following could represent the mass of the products?

• 13.3 grams

• 26.6 grams

• 3.3 grams

• 39.9 grams

An athlete injures her knee and requests a cold pack. Her coach finds a cold pack at room temperature in the First Aid kit. To activate the cold pack, the coach squeezes it several times. After 30 seconds, the cold pack then becomes cold. What kind of reaction is happening inside the cold pack?

• elastic

• exothermic

• endothermic

• evaporative

While working on a chemistry handout, Saul and Jared disagree about the following equation:

N a 2 C O 3 ( s ) + 2H C l ( a q ) → 2N a C l ( a q ) + H 2 O ( l ) + C O 2( g )

Saul says the equation is perfectly balanced but Jared disagrees. Jared says that because one of the products is a gas, its mass can’t be added to the product side since it just floats away. Which student is correct and why?

• Jared is correct because without the carbon dioxide gas, the product side is short one carbon and two oxygens.

• Jared is correct as gases are not counted in chemical equations.

• Saul is correct because the solid on the reactant side balances out the gas and liquid on the product side.

• Saul is correct because the number of each type of atom is the same on both sides of the arrow.

Which is a product in this equation? 6CO2 + 6H2O —> C6H12O6 + 6O2.

• Water

• Glucose

• Protein

• Carbon dioxide

If you wanted to design a product that cooked food without electricity, you might consider using chemicals that when mixed:

• Reacted exothermically.

• Absorbed energy.

• Reacted endothermically.

• electric

Which statement correctly describes how the following chemical equation violates the law of conservation of mass?

H2 + O2 → 2HO2

• There are more oxygen atoms on the right side of the arrow then on the left side.

• There are more hydrogen atoms on the right side of the arrow then on the left side.

• There are more hydrogen atoms on the left side of the arrow then on the right side.

• There are the same number of hydrogen atoms on the left side of the arrow as there are on the right side.

To smelt iron, the metal ore is heated with carbon monoxide to produce pig iron. Identify which chemical equation agrees with the Law of Conservation of Mass for this chemical process.

• Fe2O3 + CO → Fe + CO2

• 2Fe2O3 + CO → 4Fe + CO2

• 2Fe2O3 + 3CO → 4Fe + CO2

• Fe2O3 + 3CO → 2Fe + 3CO2

"Meals, Ready to Eat" are an instant hot meal developed by the U.S. military for troops. The meal heats up when water is added to the magnesium metal tray because the chemical reaction between water and magnesium is an _________.

• evaporation reaction

• energy conserving reaction

• endothermic reaction

• exothermic reaction

Which of the following statements is true regarding the Law of Conservation of Mass?

• It accounts for the fact that in a chemical equation the mass of the products has to be equal to the mass of the reactants.

• It reinforces the idea that atoms are the fundamental building block of matter.

• All of these are true.

• All of these are true.