Chemistry

Question 0

Organic Compounds

Answer 0

Those containing the element Carbon

*except: CO, CO2, HCO3-, CO3 2-

Question 1

Element vs Compound

Answer 1

• Element: Lead (Pb)

* Compound: Formaldehyde (HCHO)

Question 2

Inorganic Compounds

Answer 2

All other compounds e.g. CO2, H2O, NH3, H2S

Question 3

Atomic number

Answer 3

• number of protons in the nucleus of an element

* all isotopes of an element have the same atomic number

Question 4

Atomic mass

Answer 4

Total number of nucleons (protons + neutrons) in the nucleus

Question 5

Isotopes

Answer 5

Atoms of an element that have the same number of protons but a different number of neutrons (same atomic #, different atomic mass)

Question 6

Molecular formula

Answer 6

Shows the actual number of atoms of each element present in a molecule

Question 7

Molecular weight

Answer 7

The sum of the atomic weights for each molecule

*useful for converting btw moles & g

Question 8

how many moles of calcium chloride (CaCl2) are present in 15.0g of CaCl2?

Answer 8

40.08 + (2 x 35.45) = 110.98

(1 mol/ 110.98 g CaCl2) x 15g = 0.135 mol CaCl2

Question 9

A packet contains 3g of sugar formula (C12H22O11). How many moles?

Answer 9

(12x12)+(1x22)+(11x16)=342 g

(1mol/ 342g) x 3g = 0.0088 moles

Question 10

What’s molarity of 1mg of RDX (C3H6N6O6) in 20mL of water?

Answer 10

(12x3)+(6x1)+(6x14)+(16x6)= 222 g

(1mg/20mL) x (g/1000mg) x (mol/222g) x (1000mL/1L)= 0.000225 M

Question 11

Molarity

Answer 11

The number of moles of solute dissolved in one liter of solution

M= moles of solute/ liter of solution
= moles/liter

Question 12

Normality

Answer 12

Number of equivalents of solute in 1 L of the solution, N

• Number of equivalents= mass/ (molecular weight/charge on dissociated species)
• Normality= Number of equivalents /volume of solution in liters

Question 13

Calculate the normality of a 1L solution of nitric acid (80μg) HNO3,
HNO3-> H+ + NO3-

Answer 13

*Mass= 80μg x (1mg/10^3 μg) x (g/10^3 mg) = 80 x 10^-6
Mol weight of HNO3= 1+14+(163)= 63 g/mol
*# of equivalents= mass/(mol weight/charge)
80x10^-6g/(63 g/mol/ 1)= 1.269x 10^-6
*normality= #of equivalents/volume
1.269x10^-6/1 = 1.3 x 10^-6 N

Question 14

Calculate the normality for a 2L solution containing 3mg AlCl3,
AlCl3-> Al2+ + 3Cl-

Answer 14

*Mass= 3mg x (g/1000mg)= 3x10^-3 g
*mol weight of AlCl3= [26.98+ (35.45 x 3)]= 133.33 g/mol
*# of equivalents= mass/ (mol weight/charge)
3x10^-3 g/ (133.33/3)= 6.75 x 10^-5
*normality= #of equivalents/volume
6.75 x 10^-5/ 2L = 3.38 x 10^-5 N

Question 15

What’s the normality of 10mg of calcium chloride (CaCl2) in 3L,
CaCl2-> Ca2+ + 2Cl-

Answer 15

*mass= 10mg x (g/1000mg)= 10 x 10^-3
*mol weight= 40.08+ (35.45x2)= 110.98 g/mol
*#of equivalents= mass/ (mol weight/charge)
10x10^-3 g/ (110.98/2) = 1.80 x 10^-4
*normality= #of equivalents/ volume
1.80 x 10^-4/ 3= 6.0071 x 10^-5 N

Question 16

Combustion of Propane- how many g of oxygen are needed to burn 100g of propane?

Answer 16

• form balanced eqn:
  * C3H8 + O2 -> CO2 + H2O
  * C3H8 + 5O2 -> 3CO2 + 4H2O
• calculate mol weight of C3H8 & O2:
  * (3x12)+(8x1)= 44 g/mol
  * (2x16)= 32 g/mol
• determine # of moles of propane & oxygen
  * 100g x 1mol/44g = 2.2727 mol
  * (5mol O2/ mol C3H8) x 2.2727 mol C3H3 = 11.3635 mol O2
• 100 g C3H8 x (mol C3H8/44g) x (5mol O2/1mol C3H8) x (32gO2/molO2) = 363.6 g O2

Question 17

Calculate volume of air required to burn 100g of propane at STP (1atm, 273 K)

Answer 17

• volume of ideal gas at STP = 22.414 L (1mol)
• use mol of O2 to calculate volume:
  * 11.3635 mol O2 x (22.414L/mol)= 254.54 L O2
• convert from volume of oxygen to volume of air
  * air contains ~21% O2 by volume
  * 254.54 L x (L air/ 0.21 O2) = 1212.1 L air

Question 18

What mass of CO2 will be produced If 100g of butane (C4H10) is completely oxidized to CO2 and water?

Answer 18

• (4x12)+(10x1)= 58 g/mol C4H10
• 100g C4H10 x (1mol/58g)= 1.72 mol C4H10
• 1.72 mol C4H10 x (8mol CO2/2mol C4H10)= 6.90 mol CO2
• 12+ (2x16)= 44 g/mol CO2
• 6.90 mol CO2 x (44 g/ 1mol CO2)= 303.4 g CO2