Question

question 21
1 pts
the balanced equation for the reaction occurring when calcium nitrate solution is mixed with sodium phosphate solution is
ca(no3)2 (aq) + 2 napo4 (aq) → ca(po4)2 (s) + 2 nano3 (aq).
2 ca(no3)2 (aq) + 3 na3po4 (aq) → 2 ca3(po4)2 (s) + 6 nano3 (aq).
3 ca(no3)2 (aq) + 2 na3po4 (aq) → ca3(po4)2 (aq) + 6 nano3 (aq).
3 ca(no3)2 (aq) + 2 na3po4 (aq) → ca3(po4)2 (s) + 6 nano3 (aq).
3 cano3 (aq) + na3po4 (aq) → ca3po4 (aq) + 3 nano3 (s).
question 22
1 pts
the reaction 2 agno3 (aq) + k2so4 (aq) → 2 kno3 (aq) + ag2so4 (s) is an example of a(an) ______ reaction.
oxidation-reduction
precipitation
acid-base
none of the above
combustion

Explanation:

Question 21

Step1: Check formula of reactants and products

Calcium nitrate is \(Ca(NO_3)_2\), sodium phosphate is \(Na_3PO_4\). Calcium phosphate \(Ca_3(PO_4)_2\) is insoluble (s), sodium nitrate \(NaNO_3\) is soluble (aq).

Step2: Balance the equation

• For \(Ca\): There are \(3Ca\) in \(Ca_3(PO_4)_2\), so we need \(3Ca(NO_3)_2\).
• For \(PO_4\): There are \(2PO_4\) in \(Ca_3(PO_4)_2\), so we need \(2Na_3PO_4\).
• For \(NO_3\): \(3Ca(NO_3)_2\) gives \(6NO_3\), and \(2Na_3PO_4\) gives \(6Na\). So we get \(6NaNO_3\).

The balanced equation is \(3Ca(NO_3)_2(aq)+2Na_3PO_4(aq)\to Ca_3(PO_4)_2(s)+6NaNO_3(aq)\)

• In an oxidation - reduction reaction, there is a transfer of electrons (change in oxidation states). Here, oxidation states of \(Ag\), \(N\), \(O\), \(K\), \(S\) do not change.
• In an acid - base reaction, there is a transfer of \(H^+\) (not the case here).
• In a combustion reaction, a substance reacts with \(O_2\) (not the case here).
• A precipitation reaction is a reaction in which an insoluble solid (precipitate) is formed. Here, \(Ag_2SO_4(s)\) is formed.

Answer:

\(3Ca(NO_3)_2(aq)+2Na_3PO_4(aq)\to Ca_3(PO_4)_2(s)+6NaNO_3(aq)\) (the fourth option)

Question 22