Chemistry Problems

 Problems

1- How many moles are in 100 g CH3COONa (C=12, H=1, O=16, Na=23)?

2- An aqueous solution contains 80 g LiCl and 120 g water. The solution density= 1.324 g/cm3. (Li = 7, O=16, Cl=35.5). Calculate the solution molarity and molality. What is the mole fraction of LiCl?

Knowing that the saturated vapor pressure of water is 43 mmHg, calculate the vapor pressure of the solution.

3- Write the type of following reactions:

a- 2HCl + Pb(CH3COO)2→ PbCl2 + 2CH3COOH 

b- CoSO4 + 6KCN → K4[Co(CN)6] + K2SO4

c- CH2=CH2 + 5/2O2→2CO2 + 2H2O

d- Mg + Cl2→ MgCl2

e- 10FeSO4 + 8H2SO4 + 2KMnO4→ 2MnSO4 + 5Fe2(SO4)3 + K2SO4 + 8H2O 

f- HCOOH + NH3→ HCOONH4

4- CH3COOH(liq)↔ CO2(g) + CH4(g) - 120,324 kcal; KP = 2.3x108 at 25oC.

a- As pressure increases amount of CH4 should ……

b- As temperature increases amount of CH4 should ……

c- The value of KC =

d- From the value of KP, one can consider the above reaction is  …….

5- 3.5 g O2, 23 g N2 and 12 g CO2 are mixed in 2.2 L cylinder at 30 oC (C=12, O=16, N=14). Calculate the pressure.

6- In the above problem, when NaOH tablets are added to absorb CO2completely, what would be the expected pressure?

7- The times of effusion of O2 and unknown gas were 42 s and 510 s, respectively. Calculate the molecular mass of the gas.

8- An aqueous solution contains 23 g HClO4 and 130 g water and it has a vapor pressure of 33.2 mmHg. The vapor pressure of water at the same temperature is 42.5 mmHg (H=1, O=16, Cl=35.5).

a- Is the solution ideal? Show how you can decide.

b- Calculate Van't Hoff factor of the given solution.

c- Calculate the degree of dissociation or association of HClO4 in this solution.

9- A solution contains 20 g urea (NH2CONH2) and 93 g water (H=1, C=12, O=16, N=14). Knowing that the molal depression constant of water is 1.9 oC, calculate the freezing point of this solution at the normal atmospheric pressure.

10- Calculate H for the reaction:

H2(g) + O2(g)→H2O2(liq)

Given that:

H2(g) + 1/2 O2(g)→H2O(liq); H = -kcal

H2O2(liq)→H2O(liq) + 1/2 O2(g) ; H = -23.5 kcal

11- A 10 wt% alloy of Cu in Ag melts at 876 oC. Pure Ag melts at 961 oC. What is the molal freezing point depression constant for Ag. (Ag = 107.9, Cu= 63.55).