Chemistry 4B

Which products would balance the equation below?

CaCl₂ + 2Li →

• LiCl + Ca

• Li₂Cl + Ca

• 2LiCl + Ca

Which chemical reaction supports the law of conservation of mass?

• H₂O → H₂ + O₂

• H₂O → 2H₂ + O₂

• H₂O → H₂+2O₂

• 2H₂O → 2H₂+O₂

A compound containing lithium and sulfur reacts with a compound containing aluminum and iodine. Which best describes the elements present in the products of this reaction?

• lithium and iodine

• aluminum and sulfur

• aluminum, sulfur , and iodine

• lithium, sulfur , aluminum, and iodine

A chemical reaction occurs in a sealed test tube. As the result of the reaction, 24 grams of product are produced. Which is most likely true?

• The mass of the reactants was 24 grams.

• The mass of the reactants was less than 24 grams.

• The mass of the reactants was more than 24 grams.

• The mass of the reactants is not related to the 24 grams of product.

Max recorded the notes below as he completed an experiment in science class.

20 grams of a solute was added to 100 grams of a liquid substance.

The solute completely dissolved.

The total mass of the resulting solution was 120 grams after the experiment was complete.

Which best explains how the law of conservation of mass was demonstrated in the experiment?

• The solute completely dissolved in the liquid.

• The liquid was chemically changed by the addition of the solute.

• Some of the mass of the solute was lost during the experiment.

• The mass of the resulting solution was equal to the mass of the solute and liquid.

Which best explains why the total mass of the product(s) would be less than the total weight of the reactant(s) after a chemical reaction?

• A physical change occurred.

• Atoms involved in the reaction lost mass.

• Precipitates were created in the new solution.

• Gases were released to the atmosphere.

Which best explains how the chemical reaction shown below follows the law of conservation of mass?

2H₂ + O₂ → 2H₂O

• The hydrogen and oxygen molecules combine to form water.

• Hydrogen and oxygen are held together by strong chemical bonds.

• There are hydrogen and oxygen atoms on both sides of the equation.

• The same number of hydrogen and oxygen atoms are on both sides of the equation.

The compound ammonia is composed of nitrogen and hydrogen atoms. If two atoms of nitrogen completely react with six atoms of hydrogen to form two molecules of ammonia, which best describes the number of hydrogen atoms present in the two molecules of ammonia?

• two hydrogen atoms

• four hydrogen atoms

• six hydrogen atoms

Element X reacts with element Y to form 250 g of XY. If no reactants are left over, which are most likely the amounts of X and Y in the reaction?

• 75 g of X and 175 g of Y

• 95 g of X and 115 g of Y

• 100g of X and 200 g ofY

• 150 g of X and 300 g ofY

Which is a balanced chemical equation according to the law of conservation of mass?

• CH₄ + O₂ → CO₂ + 2H₂O

• CH₄ + O₂ → 2CO₂ + H₂O

• CH₄ + 2O₂ → CO₂ + 2H₂O

• 2CH₄ + O₂ → CO₂ + 2H₂O