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In which chemical equation is the number of atoms in the reactants the same as the number of atoms in the products?(1 point)

CO2 + H2O → CH2OH + O2
CO 2 + H 2 O → CH 2 OH + O 2

Li2CO3 → LiO + CO2
Li 2 CO 3 → LiO + CO 2

Zn + 2HCl → H2 + ZnCl2
Zn + 2HCl → H 2 + ZnCl 2

CH4 + O2 → CO2 + 2H2O

9 answers

To determine which chemical equation has the same number of atoms in the reactants as in the products, we need to balance the number of each type of atom on both sides of the equation.

  1. CO2 + H2O → CH2OH + O2

    • Reactants:
      • C: 1 (in CO2)
      • O: 3 (2 in CO2 + 1 in H2O)
      • H: 2 (in H2O)
    • Products:
      • C: 1 (in CH2OH)
      • O: 3 (1 in CH2OH + 2 in O2)
      • H: 2 (in CH2OH)
    • Total atoms on both sides: 6 (1C + 3O + 2H)

  2. Li2CO3 → LiO + CO2

    • Reactants:
      • Li: 2 (in Li2CO3)
      • C: 1 (in Li2CO3)
      • O: 3 (in Li2CO3)
    • Products:
      • Li: 1 (in LiO)
      • O: 1 (in LiO) + 2 (in CO2) = 3
      • C: 1 (in CO2)
    • Total atoms: 6 on the left (2Li + 1C + 3O) vs 5 on the right (1Li + 1C + 3O).

  3. Zn + 2HCl → H2 + ZnCl2

    • Reactants:
      • Zn: 1
      • H: 2 (from 2HCl)
      • Cl: 2 (from 2HCl)
    • Products:
      • Zn: 1 (in ZnCl2)
      • H: 2 (in H2)
      • Cl: 2 (in ZnCl2)
    • Total atoms: 5 on both sides (1Zn + 2H + 2Cl).

  4. CH4 + O2 → CO2 + 2H2O

    • Reactants:
      • C: 1 (in CH4)
      • H: 4 (in CH4)
      • O: 2 (in O2)
    • Products:
      • C: 1 (in CO2)
      • H: 4 (in 2H2O)
      • O: 3 (2 in 2H2O + 1 in CO2)
    • Total atoms: 7 on the left (1C + 4H + 2O) vs 8 on the right (1C + 4H + 3O).

The only equation where the number of atoms in the reactants equals the number in the products is:

Zn + 2HCl → H2 + ZnCl2.

Which statement is true regarding a chemical reaction?(1 point)
Responses

The total number of atoms changes, so mass is conserved in the reaction.
The total number of atoms changes, so mass is conserved in the reaction.

The total number of atoms does not change, so mass is conserved in the reaction.
The total number of atoms does not change, so mass is conserved in the reaction.

Even if the total number of atoms changes, mass may not be conserved in the reaction.
Even if the total number of atoms changes, mass may not be conserved in the reaction.

Even if the total number of atoms does not change, mass may not be conserved in the reaction.

The correct statement regarding a chemical reaction is:

The total number of atoms does not change, so mass is conserved in the reaction.

This reflects the law of conservation of mass, which states that in a chemical reaction, the total mass of the reactants must equal the total mass of the products, meaning that the number of atoms is conserved throughout the reaction.

Use the equation and the table to answer the question.

FeCl3 + 3H2O → Fe(OH)3 + 3HCl

Element Mass of an Atom (amu)
Fe 56
Cl 35
H 1
O 16
Iron chloride and water react according to the equation shown. The table shows the atomic masses of the elements involved in the reaction. What is the total mass of the reactants?

(1 point)
Responses

179 amu
179 amu

161 amu
161 amu

215 amu
215 amu

108 amu

To calculate the total mass of the reactants in the equation:

\[ \text{FeCl}_3 + 3\text{H}_2\text{O} \rightarrow \text{Fe(OH)}_3 + 3\text{HCl} \]

we need to find the mass of each reactant based on the given atomic masses.

  1. For FeCl₃:

    • Fe: 1 atom × 56 amu = 56 amu
    • Cl: 3 atoms × 35 amu = 3 × 35 = 105 amu
    • Total mass for FeCl₃ = 56 + 105 = 161 amu

  2. For 3H₂O:

    • H: 2 atoms per H₂O × 3 H₂O = 6 atoms × 1 amu = 6 amu
    • O: 1 atom per H₂O × 3 H₂O = 3 atoms × 16 amu = 48 amu
    • Total mass for 3H₂O = 6 + 48 = 54 amu

  3. Total mass of the reactants:

    • Total mass = Mass of FeCl₃ + Mass of 3H₂O
    • Total mass = 161 amu + 54 amu = 215 amu

The total mass of the reactants is 215 amu.

In a chemical reaction, two molecules with a total mass of 76 amu react to form a single molecule. What is the mass of the molecule that is formed?(1 point)
Responses

38 amu
38 amu

76 amu
76 amu

152 amu
152 amu

228 amu

In a chemical reaction, the law of conservation of mass states that mass is neither created nor destroyed. Therefore, the total mass before the reaction must be equal to the total mass after the reaction.

Since the two molecules have a total mass of 76 amu, the mass of the single molecule that is formed will also be 76 amu.

So the correct response is:

76 amu.

are all of them right

In the context of the problem you presented:

  • The total mass of the reactants (76 amu) should equal the mass of the product (the single molecule formed) due to the law of conservation of mass. Therefore, the mass of the molecule formed is 76 amu.

So, 76 amu is the only correct answer from the options you provided.

To clarify the other options:

  • 38 amu: Not correct, as that would imply a loss of mass.
  • 152 amu: Not correct, as that would imply a gain of mass that doesn't occur.
  • 228 amu: Also not correct, for the same reason as above.

In summary, only 76 amu is the correct answer, and the other options are not valid in this context.