section 2 review\nkey ideas\n1. identify which of the following is a complete and balanced chemical…
section 2 review\nkey ideas\n1. identify which of the following is a complete and balanced chemical equation:\na. h₂o → h₂ + o₂\nb. nacl + h₂o\nc. fe + s → fes\nd. caco₃\n2. determine balanced chemical equations for the following chemical reactions:\na. koh + hcl → kcl + h₂o\nb. nahco₃ → h₂o + co₂ + na₂co₃\nc. pb(no₃)₂ + ki → kno₃ + pbi₂\n3. explain why balancing an equation requires changing the coefficients in front of chemical formulas rather than the subscripts within chemical formulas.\n4. describe the information needed to calculate the mass of a reactant or product for the following balanced equation: fes + 2hcl → h₂s + fecl₂\ncritical thinking\n5. applying concepts chlorine gas is produced by the electrolysis of sodium chloride in water in the following reaction: 2nacl + 2h₂o → cl₂ + h₂+ 2naoh. what mass of sodium chloride is needed to make 71 g of chlorine gas?
Answer
Explanation:
Step1: Identify the molar - mass of chlorine gas
The molar mass of $Cl_2$ is $M_{Cl_2}=2\times35.5\ g/mol = 71\ g/mol$.
Step2: Determine the mole ratio from the balanced equation
From the balanced equation $2NaCl + 2H_2O\rightarrow Cl_2+H_2 + 2NaOH$, the mole ratio of $NaCl$ to $Cl_2$ is $n_{NaCl}:n_{Cl_2}=2:1$.
Step3: Calculate the moles of $Cl_2$
Given the mass of $Cl_2$ is $m_{Cl_2} = 71\ g$. Using the formula $n=\frac{m}{M}$, the number of moles of $Cl_2$ is $n_{Cl_2}=\frac{m_{Cl_2}}{M_{Cl_2}}=\frac{71\ g}{71\ g/mol}=1\ mol$.
Step4: Calculate the moles of $NaCl$
Since $n_{NaCl}:n_{Cl_2}=2:1$, when $n_{Cl_2} = 1\ mol$, $n_{NaCl}=2\ mol$.
Step5: Calculate the mass of $NaCl$
The molar mass of $NaCl$ is $M_{NaCl}=23 + 35.5=58.5\ g/mol$. Using the formula $m = n\times M$, the mass of $NaCl$ is $m_{NaCl}=n_{NaCl}\times M_{NaCl}=2\ mol\times58.5\ g/mol = 117\ g$.
Answer:
117 g