DAT General Chemistry: Stoichiometry 4

Question 1

What is the mass of 3.01 × 10^23 atoms of carbon (C=12)?

Accepted Answer

6 g

Answer

3.01 × 10^23 atoms is 0.5 mol, which weighs 0.5 × 12 = 6 g.

Question 2

In 2Al + 3Cl2 → 2AlCl3, how many moles of AlCl3 form from 4 mol of Al with excess Cl2?

Accepted Answer

4 mol

Answer

The 2:2 ratio of Al to AlCl3 means 4 mol Al gives 4 mol AlCl3.

Question 3

What is the mole fraction of solute in a solution made of 2 mol solute and 8 mol solvent?

Accepted Answer

0.20

Answer

Mole fraction is 2 / (2 + 8) = 0.20.

Question 4

How many grams of NaOH are needed to make 500 mL of a 2.0 M solution (NaOH=40)?

Accepted Answer

40 g

Answer

0.5 L × 2.0 mol/L = 1.0 mol NaOH, which is 40 g.

Question 5

If 10 g of CaCO3 (molar mass 100) decomposes, how many moles of CaO form (1:1 ratio)?

Accepted Answer

0.10 mol

Answer

10 g / 100 g/mol = 0.10 mol CaCO3, giving 0.10 mol CaO.

DAT Practice Test