Multiple Choice
Consider the unbalanced chemical equation: C_2H_5OH + O_2 → CO_2 + H_2O. What is the total number of oxygen atoms present on the left-hand side of this equation?
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3. Chemical Reactions
Balancing Chemical Equations
Multiple Choice
Which of the following is the balanced net-ionic equation for the reaction between Li(s) and water?
A
Li(s) + H2O(l) → LiOH(aq) + H2O(l)
B
Li(s) + 2 H2O(l) → Li2O(aq) + H2(g)
C
Li+(aq) + H2O(l) → LiOH(aq) + H2(g)
D
Li(s) + H2O(l) → Li+(aq) + OH−(aq) + 1/2 H2(g)
Verified step by step guidance1
Identify the reactants and products involved in the reaction. Lithium metal (Li) reacts with water (H2O) to form lithium hydroxide (LiOH) and hydrogen gas (H2).
Write the molecular equation for the reaction: \(\mathrm{Li(s) + H_2O(l) \rightarrow LiOH(aq) + \frac{1}{2} H_2(g)}\). Note that lithium hydroxide dissociates in water into ions.
Express the dissociation of lithium hydroxide in aqueous solution: \(\mathrm{LiOH(aq) \rightarrow Li^{+}(aq) + OH^{-}(aq)}\).
Substitute the dissociated ions into the molecular equation to write the full ionic equation: \(\mathrm{Li(s) + H_2O(l) \rightarrow Li^{+}(aq) + OH^{-}(aq) + \frac{1}{2} H_2(g)}\).
Since all species are either solids, liquids, or ions involved in the reaction, the net ionic equation is the same as the full ionic equation here: \(\mathrm{Li(s) + H_2O(l) \rightarrow Li^{+}(aq) + OH^{-}(aq) + \frac{1}{2} H_2(g)}\). This shows the actual chemical change occurring.
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