Question

PART A) Theobromine, C7H8N4O2, is a component of chocolate. It is mildly diuretic, is a mild stimulant, and relaxes the smooth muscles of the bronchi in the lungs. Because dogs metabolize it more slowly than humans, theobromine is very toxic to dogs.
If there are 0.064 g of theobromine in a 43 g chocolate bar, how many moles of theobromine are there?
a) 1.5 x 10−3 moles
b) 3.55181 x 10−4 moles
c) 3.6 x 10−4 moles
d) 12 moles
PART B) Calculate the molarity (M) of 151.1 g of H2SO4 in 1.405 L of solution.
Express your answer to four significant figures.
part c) Sodium hydroxide, NaOH, is a strong base that is used in industrial synthesis and processes such as making paper.
What is the mass of 2.30 ×1022 molecules of NaOH (Molar mass = 40.0 g/mol)?
Express the mass in grams to three significant figures.

Answer 1

Answer:

a. 3,6x10⁻⁴ moles

b. 1,096M

c. 1,53 g of NaOH

Explanation:

a. Theobromine has a molar mass of:

C: 12,01×7= 84,07 g/mol

H: 1,01×8= 8,08 g/mol

N: 14×4= 56,04 g/mol

O: 16×2= 32 g/mol

84,07 g/mol + 8,08 g/mol + 56 g/mol + 32 g/mol = 180,15g/mol. Thus, in 0,064g of theobromine are:

$0,064g * \frac{1mol}{180,15g}$ = 3,6x10⁻⁴ moles -two significant figures-

b. Molar mass of H₂SO₄ is 98,079 g/mol.

151,1g are:

$151,1g * \frac{1mol}{98,079g}$ = 1,54 moles of H₂SO₄

As molarity is moles of solute per liters of solution, molarity is:

1,54 moles of H₂SO₄ / 1,405L = 1,096 M

c. 2,30x10²² molecules of NaOH are:

2,30x10²²molecules × (1mol/6,022x10²³molecules) = 0,0382 moles of NaOH

As molar mass of NaOH is 40,04g/mol:

$0,0382 moles* \frac{40,04g}{1mol}$ = 1,53 g of NaOH

I hope it helps!