Question

1. in step 1, what was the evidence that a chemical reaction occurred?
2. in labs 3 and 8, we tested for co₂ using limewater. in which step would the product of the reaction make limewater turn cloudy?
3. which reactions were exothermic (gave off heat)?
4. in the presence of a flame, hydrogen gas will ________________________. based on this evidence, what is a chemical property of hydrogen?
5. balance the equations below and identify the type of reactions represented by each equation.

____al + __fe₂o₃ → __fe + ____al₂o₃ reaction type:
____pbcl₂ + __li₂so₄ → __pbso₄ + ____licl reaction type:
____na + __o₂ → ____na₂o reaction type:
____pb(oh)₂ → __pbo + ____h₂o reaction type:

Explanation:

Step1: Balance the first equation

For the equation \(Al + Fe_2O_3
ightarrow Fe+Al_2O_3\), balance the atoms.

• Balance \(Al\) and \(O\) atoms. Let the coefficients be \(a\), \(b\), \(c\), \(d\) for \(Al\), \(Fe_2O_3\), \(Fe\), \(Al_2O_3\) respectively.
• For \(O\) atoms: \(3b = 3d\), so \(b = d\). For \(Al\) atoms: \(a = 2d\). For \(Fe\) atoms: \(2b=c\). Let \(d = 1\), then \(a=2\), \(b = 1\), \(c = 2\).
• The balanced equation is \(2Al+Fe_2O_3

ightarrow 2Fe + Al_2O_3\). This is a single - replacement reaction (one element replaces another in a compound).

Step2: Balance the second equation

For the equation \(PbCl_2+Li_2SO_4
ightarrow PbSO_4+LiCl\)

• Balance \(Cl\) and \(Li\) atoms. Let the coefficients be \(a\), \(b\), \(c\), \(d\) for \(PbCl_2\), \(Li_2SO_4\), \(PbSO_4\), \(LiCl\) respectively.
• For \(Cl\) atoms: \(2a=d\). For \(Li\) atoms: \(2b=d\). Let \(a = 1\), then \(d=2\), \(b = 1\).
• The balanced equation is \(PbCl_2+Li_2SO_4

ightarrow PbSO_4 + 2LiCl\). This is a double - replacement reaction (the positive and negative ions of two ionic compounds exchange places).

Step3: Balance the third equation

For the equation \(Na+O_2
ightarrow Na_2O\)

• Balance \(Na\) and \(O\) atoms. Let the coefficients be \(a\), \(b\), \(c\) for \(Na\), \(O_2\), \(Na_2O\) respectively.
• For \(O\) atoms: \(2b=c\). For \(Na\) atoms: \(a = 2c\). Let \(b = 1\), then \(c = 2\), \(a=4\).
• The balanced equation is \(4Na+O_2

ightarrow 2Na_2O\). This is a combination reaction (two or more substances combine to form a single substance).

Step4: Balance the fourth equation

For the equation \(Pb(OH)_2
ightarrow PbO+H_2O\)

• Let the coefficients be \(a\), \(b\), \(c\) for \(Pb(OH)_2\), \(PbO\), \(H_2O\) respectively.
• For \(Pb\) atoms: \(a = b\). For \(O\) and \(H\) atoms: \(2a=b + c\). Let \(a = 1\), then \(b = 1\), \(c = 1\).
• The balanced equation is \(Pb(OH)_2

ightarrow PbO+H_2O\). This is a decomposition reaction (a single compound breaks down into two or more simpler substances).

Answer:

• \(2Al+Fe_2O_3

ightarrow 2Fe + Al_2O_3\), Reaction type: Single - replacement reaction

• \(PbCl_2+Li_2SO_4

ightarrow PbSO_4 + 2LiCl\), Reaction type: Double - replacement reaction

• \(4Na+O_2

ightarrow 2Na_2O\), Reaction type: Combination reaction

• \(Pb(OH)_2

ightarrow PbO+H_2O\), Reaction type: Decomposition reaction