Answer:
D) Lead (II) hydroxide is least soluble because the hydroxide ions in water decrease the dissociation of the ions due to the common ion effect.
Explanation:
If it is blue litmus paper, it will remain blue. If it is red litmus paper, it will remain red. Water is neither an acid nor a base so it will not change the litmus paper.
Answer:
74,67 gr/mol
Explanation:
At STP 1 mole of an ideal gas has volume of 22,4 L. Since we know the volume of the gas we can find the number of moles of the gas. (300 mL=0,3 L)
n=0,3L/22,4 L=0,01339 mol
Since we know weight of the gas as 1 g, we can find the molecular weight as;
MW=1 g/0,01339 mol =74,67 gr/mol
Answer:
We could do two 1:50 dilutions and one 1:4 dilutions.
Explanation:
Hi there!
A solution that is 1000 ug/ ml (or 1000 mg / l) is 1000 ppm.
Knowing that 1 ppm = 1000 ppb, 100 ppb is 0.1 ppm.
Then, we have to dilute the stock solution (1000 ppm / 0.1 ppm) 10000 times.
We could do two 1:50 dilutions and one 1:4 dilutions (50 · 50 · 4 = 10000). Since the first dilution is 1:50, you will use the smallest quantity of the stock solution (if we use the 10.00 ml flask):
First step (1:50 dilution):
Take 0.2 ml of the stock solution using the third dispenser (20 - 200 ul), and pour it in the 10.00 ml flask. Fill with water to the mark (concentration : 1000 ppm / 50 = 20 ppm).
Step 2 (1:50 dilution):
Take 0.2 ml of the solution made in step 1 and pour it in another 10.00 ml flask. Fill with water to the mark. Concentration 20 ppm/ 50 = 0.4 ppm)
Step 3 (1:4 dilution):
Take 2.5 ml of the solution made in step 3 (using the first dispenser 1 - 5 ml) and pour it in a 10.00 ml flask. Fill with water to the mark. Concentration 0.4 ppm / 4 = 0.1 ppm = 100 ppb.
<span>The number of moles of Cl- ions needed to combine completely with 0.25 mole of Mg+2 ions is:
0.50.</span>
