## Some practice probs (not from HW) to study for the test!

Julia Mazzucato 4D
Posts: 64
Joined: Fri Aug 30, 2019 12:17 am

### Some practice probs (not from HW) to study for the test!

Hi guys, I wanted to create a thread for some good practice problems from the TB (not part of the HW questions) to study for the test in week 2. Feel free to share any good practice probs you find so we can all study together!

Molarity/Dilution Practice Problems

G.3) Identify the following mixtures as homogeneous or heterogeneous, and suggest a technique for separating their components:
(a) oil and vinegar
(b) chalk and table salt
(c) salt water

G.6) A chemist prepares a solution by dissolving 1.734 g of NaNO3 in enough water to make 250.0 mL of solution.
What molar concentration of sodium nitrate should appear on the label?
If the chemist mistakenly uses a 500.0-mL volumetric flask instead of the 250.0-mL flask, what molar concentration of sodium nitrate will the chemist actually prepare?

G.12) A student investigating the properties of solutions containing carbonate ions prepared a solution containing 8.124 g of Na2CO3 in a flask of volume 250.0 mL. Some of the solution was transferred to a buret. What volume of solution should be dispensed from the buret to provide
a) 5.124 mmol Na2CO3
b) 8.726 mmol Na1?

G.18) The ammonia solution that is purchased for a stockroom has a molarity of 15.0 mol/L
a) Determine the volume of 15.0 M NH3(aq) that must be diluted to 250. mL to prepare 0.720 M NH3(aq)
b) An experiment requires 0.050 M NH3(aq). The stockroom manager estimates that 8.10 L of the base is needed. What volume of 15.0 M NH3(aq) will be required for the preparation?

Good luck guys!

Julia Mazzucato 4D
Posts: 64
Joined: Fri Aug 30, 2019 12:17 am

### Re: Some practice probs (not from HW) to study for the test!

G.3) a) heterogenous, they will separate on their own and you can take the oil from the top. b) heterogenous, use a sifter to separate larger salt crystals from fine chalk dust. c) homogenous, boil the water to evaporate it from the salt.
G.6) a) 0.08161 M, b) 0.04080 M
G.12) a) 16.72 mL, b) 14.24 mL
G.18) a) 12mL, b) 0.027 L or 27 mL

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