How much of which should you measure out to make 100 mL of a 0.5% aqueous solution of sucrose?
0.5 gram of sucrose
You have the containers in front of you. You need 100 mL of 2% lactose. How much of what do you use?
one way: 2 grams of lactose powder; q.a. 100 mL with water
faster way: 50 mL of 4% lactose + 50 mL of water.
Jason added 100 mL of X to 100 mL of water and obtained a sucrose solution that was 5%. What was the concentration of X?
CV=CV: 5% x 200 mL = X x 100 mL
X = (5% x 200)/100 = 10%
You make 1% solutions of both NaCl (58 daltons) and sucrose (342 daltons). Which one is of the higher molarity?
NaCl because there are more molecules in 1 gram of NaCl than there are in 1 gram of sucrose.
1% = 1 gram in 100 mL; or 10 grams in a liter
Molar = number of molecular weights added to a liter.
Thus 1% NaCl is 10 grams/58 (= 0.17M), while 1% sucrose is 10 gram/342 (= 0.03M)
(Fill in the blanks with either "Percent solutions" or "Molar solutions") ___A____ are based on the numbers of molecules added, while ____B____ are based on the total mass of stuff dissolved.
A = molar solutions; B = percent solutions
Jimmy diluted some seawater (3.3%) thusly: He added 10 mL of seawater to 990 mL of pure water. What was the final percent solution of the seawater?
CV=CV: 3.3% x 10 mL = X x 1000 mL
X = (3.3% x 10)/1000 = 0.033%
Wilbie has just bought a new prized fish for his marine aquarium (marine = sea water). He needed to make 20 liters (how many mL is that?) of artificial sea water which is 3.3% sea salt. How much sea salt should he dissolve in the 20 liters?
Let's see: he needs 3.3 grams per 100 mL, so
3.3 grams is to 100 mL as X is to 20,000 mL
X = 20,000 x (3.3 grams/100) = 660 grams
This question will replace any two of the previous. In five minutes you will need 100 mL of 5% ribose. Searching the stockroom you find two bottles. One contains about 3 grams of crystalline ribose, and the other contains about 200 mL of 3% ribose. How much of which do you use?
The first thing you notice is that you don't have enough crystalling ribose: you need 6 grams.
The second thing you notice is that what you want is more concentrated than the 3%. Thus neither stock item ALONE contains enough to get you to where you want to go.
Thus you must need to add some crystalline ribose to the 3% ribose to make up the needed additional 2%.
100 mL of 2% would require adding 2 grams of solid ribose, which you have.
So, take 2 grams of solid ribose and make it up to 100 mL with the 3% ribose to get your 100 mL of 5% ribose.