Ch 3 Composition of Solutions & Substances

Question 1

Find the Molar Mass (formula mass) of Ibuprofen C13H18O2

Answer 1

C: 12.01 x 13 =
H: 1.008 x 18 =
O: 16.00 x 2 =
Add the sum together

206.27 amu (atomic mass unit)

Question 2

What is the formula mass (amu) of calcium phosphate? Ca3(PO4)2

Answer 2

310.18 amu

Question 3

What is a mole?

Answer 3

A unit to measure atoms & molecules

Question 4

Avogadro’s Number

Answer 4

6.022 x 10^23

Question 5

How many moles are there in 17g of Carbon?

Answer 5

1.4 mol of C

Question 6

How many atoms are there in 3.00 moles of Carbon?

Answer 6

1.81 x 10^24 C atoms

Question 7

How many atoms are there in 12g of Phosphorus?

Answer 7

2.3 x 10^23 atoms of P

Question 8

What is the formula to find moles?

Answer 8

number of mol = mass divided by molar mass
n = m/M

Question 9

Formula for Percent Composition

Answer 9

% of A = (mass A divided by total mass of compound) × 100

Question 10

A 24.81 g sample of a gaseous compound containing only carbon, oxygen, and chlorine is determined to contain 3.01 g C, 4.00 g O, and 17.81 g Cl. What is this compound’s percent composition?

Answer 10

C = 12.1%
O = 16.1%
Cl = 71.76%

Question 11

Find the Empirical Formula: 1.71 g C and 0.287 g H.

Answer 11

C: (1.71 x 12.01) = 0.142 divided by 0.142 = 1
H (0.287 x 1.008) = 0.284 divided by 0.142 = 2

Empirical Formula: CH2
Note: divided by the smallest number of moles

Question 12

What is the difference between molecular & empirical formula?

Answer 12

Molecular: how many atoms of each element are in a compound
Empirical: simplified version of the molecular formula

Ex: N2O4 -> NO2

Question 13

The relative amount of a given solution component is known as its _____________.

Answer 13

Concentration

Question 14

A solution in which water is the solvent is called an ______________.

Answer 14

Aqueous solution

Question 15

What is Molarity (M)?

Answer 15

A unit of concentration

Question 16

What is the formula for Molarity?

Answer 16

M = mol solute divided by L solution

Question 17

Solute

Answer 17

The substance being dissolved (ex: salt)

Question 18

Solvent

Answer 18

The substance used to make the solute dissolve (ex: salt + water, water is the solvent)

Question 19

Solution

Answer 19

The result of the solute and the solvent being mixed together (ex: salt + water = salt water (solution))

Question 20

Mass Percentage

Answer 20

mass percentage = (mass of component divided by mass of solution) x 100

Question 21

A 5.0-g sample of spinal fluid contains 3.75 mg (0.00375 g) of glucose. What is the percent by mass of glucose in spinal fluid?

Answer 21

(0.00375 g) divided by (5.0) = 7.5 x 10^-4

(7.5 x 10^-4)(100) = 0.075%

Question 22

Volume Percentage

Answer 22

Volume Percentage = (volume solute divided by volume of solution) x 100