Balancing Chemical Reactions and the Law of Conservation of Mass

What is the primary principle behind the law of conservation of mass?

• The total energy of the system remains constant.

• The total mass of reactants equals the total mass of products.

• The total volume of reactants equals the total volume of products.

• The total number of molecules remains constant.

Tags

NGSS.MS-PS1-5

In the context of balancing chemical equations, what does it mean if the number of atoms of an element on the left side equals the number on the right side?

• The reaction is exothermic.

• The equation is balanced.

• The reaction is spontaneous.

• The reaction is endothermic.

Tags

NGSS.HS-PS1-7

When balancing chemical equations, why can't you change the subscripts in a compound?

• Because it would change the identity of the compound.

• Because it would change the pressure of the reaction.

• Because it would change the state of the compound.

• Because it would change the temperature of the reaction.

What is the role of coefficients in a chemical equation?

• They indicate the temperature at which the reaction occurs.

• They indicate the pressure at which the reaction occurs.

• They indicate the number of atoms in a molecule.

• They indicate the number of molecules or moles of a substance.

In the equation 2 Na + Cl2 → 2 NaCl, what does the coefficient '2' in front of NaCl indicate?

• There are two atoms of chlorine in the reaction.

• There are two atoms of sodium in the reaction.

• There are two moles of sodium in the reaction.

• There are two molecules of sodium chloride produced.

When balancing the equation NaBr + Cl2 → NaCl + Br2, what is the correct coefficient for NaBr?

• 2

• 1

• 3

• 4

Tags

NGSS.MS-PS1-5

Which element should you balance first in a complex chemical equation?

• Elements that are in their elemental form.

• Elements that are gases.

• Elements that are in compounds on both sides of the equation.

• Elements that are metals.

In a combustion reaction, why might you see higher numbers as coefficients?

• Because combustion reactions always produce carbon dioxide.

• Because combustion reactions often involve large amounts of reactants and products.

• Because combustion reactions are always exothermic.

• Because combustion reactions always produce water.

What should you do if you notice high numbers as coefficients in a non-combustion reaction?

• Check if the numbers can be divided by a greatest common factor.

• Add more reactants to the equation.

• Change the subscripts in the compounds.

• Increase the temperature of the reaction.

In the combustion reaction C7H16 + O2 → CO2 + H2O, what is the correct coefficient for O2 to balance the equation?

• 11

• 7

• 8

• 16