Question

1. What are the spectator ions if 250.mL of 1.0M aqueous magnesium bromide is added to 125 mL of 2.0M aqueous ammonium carbonate?

2. What is the net ionic equation for the reaction that occurs when aqueous calcium sulfide is mixed with aqueous sodium phosphate?

3. If 11.0 mL of hydrobromic acid solution required 18.01 mL of 0.9956 M sodium hydroxide to reach the equivalence point, what is the molarity of the hydrobromic solution?

4. A gas is contained in a cylinder with a movable piston. The initial gas pressure inside the cylinder is P1, and the initial gas volume is V1. What is the new gas pressure (P2) if the volume of the gas is decreased by half at constant temperature?

*Please help me solve these problems.

Answer 1

1.)

moles of MgBr2 = 0.250 x 1.0 = 0.250

moles of (NH4)2CO3 = 0.125 x 2 = 0.250

MgBr2 + (NH4)2CO3   -----------> MgCO3 (s) + 2 NH4Br .

here

NH4+ and Br- ions are spectators

2)

3 CaS (aq) + 2 Na3PO4 (aq) -----------> Ca3(PO4)2 (s) + 3 Na2S (aq)

Net ionic :

3 Ca²⁺ (aq) + 2 PO₄^3- (aq)   ------------> Ca₃(PO₄)₂ (s)

3.)

HBr +   NaOH    ----------> NaBr + H2O

moles of HBr = moles of NaOH

11.0 x M = 18.01 x 0.9956

M = 1.63

moalarity of HBr = 1.63 M

4.)

P1 = P1 , V1 = V1

V2 = V1 / 2

P1 V1 = P2 V2

P1 x V1 = P2 x V1 / 2

P2 = 2 P1

new pressure P2 = 2 P1