CHE140 Modules 4&5

Solving moles

100

What is the formula for calculating moles from the number of atoms?

n=N/N_A

200

What is the mass(g) of aluminium in 6.73 moles?

182g of Al

300

What is Avagadro's constant?

6.022 x 10²³

400

How many moles are there in 3.45 x 10²⁴ atoms of gold?

5.73 mol Au

500

How many atoms are there in 22.9 mol of Hg?

1.38 x 10²⁵ atoms

Unit conversion

100

3.55 kg to grams.

3550 g or 3.55 x 10³g

200

248 cm to nm

2,480,000,000 nm or 2.48 x 10¹⁰ nm

300

5.88 dL to litres

0.588 L or 5.88 x 10^-1 L

400

1.88 x 10^-6 g to ug 

1.88 ug

500

1.15 x 10^-10 m to picometers

115 pm

Empirical formulas

100

Determine the empirical formula of the compound composing of 1.78g of N and 4.05g of O.

NO₂

200

Calculate the empirical formula of the compound with 1.651g of Ag and 0.1224g of O

Ag₂O

300

Calculate the empirical formula of the compound with 2.128g of Be, 7.557g of S, and 15.107g of O

BeSO₄

400

Calculate the empirical formula of the compound containing: 54.50% C, 13.73% of H, and 31.77% of N by mass percent.

C₂H₆N

500

Calculate the empirical formula of a compound containing: 71.98% C, 6.71% H and 21.31% O by mass percent.

C₉H₁₀O₂