Balancing Chemical Equations
Which of the following is a chemical equation that accurately represents what happens when sulfur and oxygen react to form sulfur trioxide? A. Sulfur and oxygen react to form sulfur trioxide. B. S and O₂ produce SO₃ C. S + O₂ → SO₃ D. 2S + 3O₂ → 2SO₃
2S + 3O₂ → 2SO₃
Balance the following chemical equation. Zn + HCl → ZnCl + H₂
2Zn + 2HCl → 2ZnCl + H₂
Methane (CH₄) burns in oxygen gas to form water and carbon dioxide. What is the correct balanced chemical equation for this reaction? A. CH₄ + O → H₂O + CO₂ B. CH₄ + 4O₂ → 2H₂O + CO₂ C. CH₄ + O₂ → H₂O + CO₂ D. CH₄ + 2O₂ → 2H₂O + CO₂
CH₄ + 2O₂ → 2H₂O + CO₂
What is the balanced chemical equation for the reaction represented in Figure 7-2?
CH₄ + 2O₂ → 2H₂O + CO₂
Hydrochloric acid, HCl, is added to solid NaOH. After the reaction is complete, NaCl and water remain. What are the products of this chemical reaction?
NaCl and H₂O
A student balanced the chemical equation Mg + O₂ → MgO by writing Mg + O₂ → MgO₂ Was the equation balanced correctly? Explain your answer. If the equation was not balanced correctly, write the correctly balanced equation.
No. Because it was balanced by changing a subscript instead of changing coefficients. 2Mg + O₂ → 2MgO
2 Zn + HCl → ZnCl + H₂ In the chemical equation above, the total number of atoms is the same on both sides of the arrow. If the total number of atoms on the left side of an equation equals the total number of atoms on the right side of the equation, does this mean that the equation is balanced? Explain your answer.
No; the total number of atoms must be the same FOR EACH ELEMENT separately on each side of the equation .
How many of each type of atom are present on each side of the unbalanced equation in Figure 7-2?
On the left side: 1 carbon, 4 hydrogens, and 2 oxygens. On the right side: 1 carbon atom, 3 oxygens, and 2 hydrogens.
What is the purpose of balancing a chemical equation?
So we don't break the Law of Conservation of Mass.
A(An) ____________________ is the number that appears before a formula in a chemical equation.
coefficient
The statement that in chemical reactions, the total mass of the reactants equals the total mass of the products is the law of
conservation of matter
Which of the following does NOT state what the arrow means in a chemical equation? A. forms C. conserves B. produces D. yields
conserves
In an experiment, 44 g of propane were burned in oxygen, producing 132 g of carbon dioxide and 72 g of water. The mass of oxygen that was needed for the reaction was
mass reactants = mass products 44g + oxygen = 132g + 72g 44g + oxygen = 204g oxygen = 160 g
The substances that are present before a chemical reaction takes place are called
reactants
Which of the following is a balanced chemical equation for the production of NaBr from Na and Br₂? A. Na + Br₂ → NaBr B. 2Na + Br₂ → NaBr C. Na + Br₂ → 2NaBr D. 2Na + Br₂ → 2NaBr
2Na + Br₂ → 2NaBr
W reacts with X in the equation below. W + X → Y + Z According to the law of conservation of mass, how many grams of W must react completely with 225 grams of X to result in 375 grams of product?
150 g
Which of the following does NOT show the law of conservation of mass? (answer in notes) A. 24 g of Mg burn in 32 g O2 to produce 56 g of MgO. B. 24 g of Mg burn in 32g O2 to produce 8 g of MgO. C. 2 atoms of Mg react with 1 molecule of O2 to produce 2 units of MgO. D. 1 atom of Mg reacts with 1 atom of O to produce a unit of MgO that contains 2 atoms.
24 g of Mg burn in 32g O2 to produce 8 g of MgO.
If there are 4 hydrogen atoms on the left side of equation in Figure 7-2, how many hydrogen atoms must there be on the right side in order to balance this reaction?
4 hydrogen atoms
