EOG Law of Conservation of Mass

Balance the following equation 2H2 + O2⟶ __________H2O a. 2 b. 3 c. o d. 4

a. 2

Which equation demonstrates the law of conservation of mass? a. 2Al + 6HCl --> 2AlCl3 + 3H2 b. 4Al + 2HCl → 2AlCl + H2 c. Al + 2HCl → AlCl + H d. 2Al + 3HCl → 2AlCl + 3H2

a. 2Al + 6HCl --> 2AlCl3 + 3H2

Which is true of mass during a chemical reaction? a. Mass remains the same b. Mass decreases c. Mass increases d. Mass depends on the chemicals involved.

a. Mass remains the same

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? a. lithium, sulfur, aluminum, and iodine b. aluminum, sulfur, and iodine c. lithium and iodine d. aluminum and sulfur

a. lithium, sulfur, aluminum, and iodine

Which are conserved during a chemical reaction? a. mass and atoms b. atoms and molecules c. volume and mass d. molecules and volume

a. mass and atoms

Which ratio of reactants to products supports the law of conservation of mass? a. 1:0 because the mass of the reactants is completely used up during the reaction so the products have no mass after the reaction b. 1:1 because the mass of the reactants before the reaction is equal to the mass of the products after the reaction c. 1:2 because the mass of the reactants is doubled during the reaction d. 2:1 because the mass of the reactants is halved during the reaction

b. 1:1 because the mass of the reactants before the reaction is equal to the mass of the products after the reaction

A 12-gram sample of magnesium (Mg) reacts with an 18-gram sample of sulfur (S) when heated. Magnesium sulfide (MgS), a solid crystalline material, is formed. What mass of MgS is most likely produced? a. 216g b. 30g c. 60g d. 6g

b. 30g

Chemicals X and Y produce a toxic gas when mixed together in the ratio 10 g of X for every 2 g of Y. What would happen if a scientist mixing the two chemicals only had 1 g of chemical Y? a. Chemicals X and Y would create the gas until all of chemical X was used in the reaction. b. Chemicals X and Y would create the gas until all of chemical Y was used in the reaction. c. The same amount of toxic gas would be produced regardless of the amount of chemical Y available. d. Chemicals X and Y would combine in a different way and create another gas.

b. Chemicals X and Y would create the gas until all of chemical Y was used in the reaction.

Which is true of any physical or chemical reaction? a. Mass fluctuates. b. Mass is conserved. c. Mass decreases. d. Mass increases.

b. Mass is conserved.

A student mixed 10 grams of a powdery substance with 200 grams of an acid solution. A bubbly solution weighing 205 grams was formed. Which best explains why the mass of the new solution does not equal the mass of the reactants? a. The other 5 grams created a precipitate. b. The other 5 grams were released as a gas. c. The other 5 grams changed color. d. The other 5 grams weighed less in the acid.

b. The other 5 grams were released as a gas.

The equation below shows a reaction between sodium (Na) and water (H2O) 2Na+H2O⟶⟶2NaOH+H2 Which best explains why the equation is not balanced? a. There is not enough sodium hydroxide in the products. b. There is not enough water in the reactants. c. There is too much sodium in the reactants. d. There is too much hydrogen gas in the products.

b. There is not enough water in the reactants.

Which best describes a chemical reaction applying the law of conservation of mass? a. an equation which uses energy b. a balanced equation in which the reactants and products are equal c. an equation which does not use energy d. an unbalanced equation in which the reactants and products are unequal

b. a balanced equation in which the reactants and products are equal

Which is the best system to use when studying the law of conservation of mass? a. a large system to give the reaction space to occur b. a closed system to measure the mass of the reaction c. a small system to closely observe the reaction d. an open system to measure the mass of the reaction

b. a closed system to measure the mass of the reaction

During balancing equations you can not change the subscripts, you can only add _______________________ a. atoms b. coefficients c. elements d. subscripts

b. coefficients

How many methane (CH4) molecules would be needed to produce 13 carbon dioxide (CO2) molecules? CH4 + 2O2⟶⟶CO2 + 2H2O a. 52 b. 4 c. 13 d. 26

c. 13

Which chemical reaction supports the law of conservation of mass? a. H2O⟶⟶ H2 + 2O2 b. H2O⟶⟶ 2H2 + O2 c. 2H2O⟶⟶ 2H2 + O2 d. H2O ⟶⟶ H2 + O2

c. 2H2O⟶⟶ 2H2 + O2

Balance the following equation 4P + ______O2⟶2P2O5 a. 6 b. 2 c. 5 d. 3

c. 5

Which best describes how to balance the chemical equation shown below to support the law of conservation of mass? Mg + O2⟶⟶ MgO a. Add the coefficient 2 before the Mg on the left side of the equation. b. Add the coefficient 2 before the MgO on the right side of the equation. c. Add the coefficient 2 before the Mg on both sides of the equation. d. Add the coefficient 2 before the Osub2 on the left side of the equation.

c. Add the coefficient 2 before the Mg on both sides of the equation.

The left side of an equation has the a. products b. problem c. reactants d. regent

c. reactants

Balance the following equation _____Ca + O2⟶⟶ 2CaO a. 8 b. 4 c. 6 d. 2

d. 2

A teacher has 100 g of Reactant X and 150 g of Reactant Y for her class demonstration. After combining the two reactants, how much product should she have? a. 100g b. 50g c. 150g d. 250g

d. 250g

What is the total number of oxygen atoms on the reactant side of the equation shown below? CH3COOH + NaHCO3⟶⟶ CH3COONa + H2O + CO2 a. 7 b. 2 c. 3 d. 5

d. 5

If a student is chemically combining 4g of hydrogen with 2g of oxygen, what will be the mass of the product? a. 10g b. 8g c. 4g d. 6g

d. 6g

A experiment was conducted to test the law of conservation of mass. At the end of the experiment, only 82% of the mass of the initial reactants was present. The experiment was repeated three times with similar results. Which best explains why some of the mass was lost? a. The mass turned into a heavier chemical. b. The mass transformed into a liquid. c. The mass remained part of the reactant. d. The mass escaped as a gas.

d. The mass escaped as a gas.

A chemical reaction is shown below. 2H2+O2⟶ 2H2O Based on the law of conservation of mass, how much hydrogen gas is produced compared to the amount of oxygen produced? a. four times as much b. the same amount c. half as much d. twice as much

d. twice as much