DAT Chemistry - Practice Questions with Detailed Answer Which of the following interactions is the strongest?
- hydrogen bonds
- dipole-dipole forces
- hydrophobic interactions
- ionic bonds
e) London dispersion forces - Answer: Ionic bonds (complete transfer of electrons)
Hydrogen bonds are the strongest intermolecular force but not stronger than ionic What is the maximum # of electrons the d sub shell can hold?
- 2
- 6
- 10
- 14
e) 18 - Answer: 10
S = 2 P = 6
D = 10
F = 14
etc 1 / 4
Calcium chlorate (CaCrO4) is a yellow solid with a Ksp of 7.1 x 10^-4. Determine the ion product constant and whether precipitate would form when an aqueous solution contains 26mM of Ca2+ and 29 mM of CrO42- - Answer: 1. Write out reaction and IP equation: CaCrO4 (s) -> Ca2+ (aq) + CrO42- IP = [Ca2+][CrO42-]
2. Convert mM to mole and plug into equation:
IP = 0.026M x 0.029 (moves 3 decimal places) = 0.000754 = 7.54x10^-4
- Compare IP value above to Ksp.
IP > Ksp = shift left and ppt forms IP < Ksp = shift right and ppt doesn't form A container holds 4.0L of gas at 3.5 atm and a temp of 27 degrees C. If the pressure is reduced to 0.8 atm without a change in temperature, what would be the volume of the gas? - Answer: Use: P1V1/n1T1 = P2V2/n2T2 Can assume that n1 = n2 since no change in gas molecules and also for T since it is constant.Therefore, P1V1=P2V2 (3.5atm)(4.0L)=(0.8)(V2)
V2 = (3.5)(4.0)/(0.8)
V2 = 18
dividing by 0.8 = slightly larger number A NaOH solution has a molarity of 2.00M and is titrated with 75mL of 0.5M H2SO4. What volume of NaOH is needed to reach end point? - Answer: end point - colour change (equivalence point) 2 / 4
NaOH + H2SO4 -> Na2SO4 + 2H2O
- Find moles of H2SO4 = molarity x volume
= (0.5mol/L) x 0.0750 L = 0.0375 x 2 = 0.0750 mol of NaOH
Find volume of NaOH: 0.0750 mol/ 2 mol/L = 0.03650 L
What is the bond angle that exists within a molecule of SO3?
- 90
- 104.5
- 107
- 109.5
e) 120 - Answer: SO3 = trigonal planer = 120 degree bond angles
An aqueous mixture contains CuF2 and BaF2 (Ksp = 3.0x10^-6). What should be added to the solution in order to precipitate CuF2?
a) NaF
b) H2O
c) Ba(NO3)2
d) Cu(NO3)2 - Answer: Cu(NO3)2
According to the following reaction, how many grams of hydrogen gas are formed when 15g of aluminum react with the excess acid?2Al + 6HCl -> 2AlCl3 + 3H2 - Answer: 1. Determine limiting reagent. Since HCl is the acid (excess) we know Al will be limiting.
2. Find moles of Al:
mol = mass/ molar mass mol = 15g/27g/mol 3 / 4
- Find moles of hydrogen present relative to Al moles: 3 moles of H2 for every 2 Al
moles of H: moles of Al x mole ratio of H to Al
mol of hydrogen = 15/27 x 3mol H2/2mol Al Al cancels out so (15)(3)/ (27)(2)
4. Find mass of hydrogen: mol of H x molar mass
[(15)(3) / (27)(2)] x 2 (cancels out so) (15)(3)/27 Which of the following elements exists as a diatomic gas and contains a double covalent bond?
- krypton
- oxygen
- nitrogen
- bromine
e) chlorine - Answer: oxygen (must form double bond)
Also remember nitrogen must form a triple bond recall: hydrogen, nitrogen, fluorine, oxygen, iodine, chlorine, bromine are all diatomic Which of the following pairs are typically found in alkaline buffer solutions?
a) Weak base and conjugate acid
b) Weak acid and conjugate base
c) Strong base and conjugate acid
d) Strong acid and conjugate base
e) Strong acid and its conjugate acid - Answer: Weak base and its conjugate acid.
Buffers resist changes in pH and will always be a weak base or weak acid.
- / 4