Question

quiz 8.6be- counting atoms, chemical equations and the law of conservation of mass 9 of 10 possible points: 6.25 pure sodium (na) reacts violently with water (h₂o) to produce sodium hydroxide (naoh) and hydrogen gas (h₂). some of the masses of the reactants and products are shown. 2na + 2h₂o → 2naoh + 2h₂ ? + 85 g → 95 g + 10 g following the law of conservation of mass, how many grams of sodium were used in the reactants? ∘ 95 g ∘ 10 g ∘ 75 g ∘ 20 g

Explanation:

Step1: Recall Law of Conservation of Mass

The Law of Conservation of Mass states that the total mass of reactants equals the total mass of products. So, \( m_{\text{Na}} + m_{\text{H}_2\text{O}} = m_{\text{NaOH}} + m_{\text{H}_2} \).

Step2: Plug in known values

We know \( m_{\text{H}_2\text{O}} = 85\ \text{g} \), \( m_{\text{NaOH}} = 95\ \text{g} \), \( m_{\text{H}_2} = 10\ \text{g} \). Let \( m_{\text{Na}} = x \). Then:
\( x + 85 = 95 + 10 \)

Step3: Solve for \( x \)

Simplify the right side: \( 95 + 10 = 105 \). So, \( x + 85 = 105 \). Subtract 85 from both sides: \( x = 105 - 85 = 20 \).

Answer:

20 g (corresponding to the option "20 g")