Math in chemistry

Which formula is the empirical formula for ethane, C₂H₆?

• CH₃

• C₄H₁₂

• C₂H₆

• CH

Given a balanced equation representing a reaction: 2CO(g) + O₂(g) → 2CO₂(g) + energy. Which mass of O₂(g) reacts completely with 5.6 grams of CO(g) to produce 8.8 grams of CO₂(g)?

• 14.4 g

• 1.6 g

• 2.8 g

• 3.2 g

Given the balanced equation representing a reaction: 2KClO₃ → energy → 2KCl + 3O₂. What is the mass of KCl produced when 24.51 grams of KClO₃ reacts completely to produce 9.60 grams of O₂?

• 43.71 g

• 34.11 g

• 14.91 g

• 5.31 g

Tags

NGSS.HS-PS1-7

What is the gram-formula mass of Mg(NO₃)₂?

• 172 g/mol

• 134 g/mol

• 86 g/mol

• 148 g/mol

Given the balanced equation for the reaction of butane and oxygen: 2C₄H₁₀ + 13O₂ → 8CO₂ + 10H₂O + energy. How many moles of carbon dioxide are produced when 5.0 moles of butane react completely?

• 20. mol

• 10. mol

• 5.0 mol

• 40. mol

Tags

NGSS.HS-PS1-7

Given the balanced equation representing the reaction between methane and oxygen: CH₄ + 2O₂ → CO₂ + 2H₂O. According to this equation, what is the mole ratio of oxygen to methane?

• 2 grams O₂ / 1 gram CH₄

• 1 gram O₂ / 2 grams CH₄

• 2 moles O₂ / 1 mole CH₄

• 1 mole O₂ / 2 moles CH₄

One mole of bromine gas, Br₂, has a mass of

• 79.9 g

• 35.0 g

• 70.0 g

• 159.8 g

A solution contains 25 grams of KNO₃ dissolved in 200. grams of H₂O. Which numerical setup can be used to calculate the percent by mass of KNO₃ in this solution?

• 25g / 175g × 100

• 200g / 225g × 100

• 25g / 200g × 100

• 25g / 225g × 100

What is the number of moles in a 78.8-gram sample of MgCO₃ (gram-formula mass = 84.3 g/mol)?

• 0.935 mol

• 1.070 mol

• 0.843 mol

• 0.949 mol

Tags

NGSS.HS-PS1-7

Which numerical setup can be used to calculate the formula mass of C₉H₁₁NO₂?

• 12 u + 1 u + 14 u + 16 u

• 9(6 u) + 11(1 u) + 1(7 u) + 2(8 u)

• 9 u + 11 u + 1 u + 2 u

• 9(12 u) + 11(1 u) + 1(14 u) + 2(16 u)

Tags

NGSS.HS-PS1-7