Question

1. choose all that apply.

what are the two reactants?
□ co₂(g)
□ h₂o(g)
□ o₂(g)
□ c₄h₁₀(g)

1. choose the best answer.

which chemical equation demonstrates the law of conservation of mass?
○ 4h₃po₄ → 3h₂o + p₄h₁₀
○ 4nh₃ + 5o₂ → 4no + 6h₂o
○ nai + cl₂ → i₂ + nacl
○ 2no + o₂ → 2no

Explanation:

Question 5

Step1: Recall Reactants Definition

Reactants are on the left of a chemical reaction (though the reaction isn't shown, we infer common reactions). Combustion of hydrocarbons (\(C_4H_{10}\)) uses \(O_2\) as reactant. \(CO_2\) and \(H_2O\) are usually products of combustion.

Step2: Identify Reactants

\(C_4H_{10}(g)\) (butane, a hydrocarbon) and \(O_2(g)\) (oxygen) are reactants in combustion. \(CO_2\) and \(H_2O\) are products. So the two reactants are \(O_2(g)\) and \(C_4H_{10}(g)\).

Step1: Law of Conservation of Mass

Requires same number of each atom on both sides.

Step2: Analyze Each Equation

• \(4H_3PO_4 \to 3H_2O + P_4H_{10}\): Count H: Left \(4\times3 = 12\), Right \(3\times2 + 10 = 16\) → Not balanced.
• \(4NH_3 + 5O_2 \to 4NO + 6H_2O\): Count N: 4 left, 4 right. H: \(4\times3 = 12\), \(6\times2 = 12\) right. O: \(5\times2 = 10\), \(4\times1 + 6\times1 = 10\) right. Balanced.
• \(NaI + Cl_2 \to I_2 + NaCl\): Count Cl: 2 left, 1 right. Not balanced (needs coefficient 2 on NaCl and 2 on NaI).
• \(2NO + O_2 \to 2NO\): Product is same as one reactant, O not balanced (left 4 O, right 2 O).

Answer:

\(O_2(g)\), \(C_4H_{10}(g)\) (the checkboxes for \(O_2(g)\) and \(C_4H_{10}(g)\) should be selected)

Question 6