Answer:
0.015 moles
Explanation:
- One mole of a compound contains molecules equivalent to the Avogadro's constant, 6.022 × 10^23.
- That is, 1 mole of a compound will have 6.022 × 10^23 molecules.
In our case, We are given 8.96 x 10^21 molecules of KBr
We need to find the number of moles in 8.96 x 10^21 molecules
1 mole of KBr = 6.022 × 10^23 molecules.
8.96 x 10^21 molecules = ?
Therefore;
(1 × 8.96 x 10^21 molecules ) ÷ 6.022 × 10^23 molecules.
= 1.488 × 10^-2 moles
= 0.01488 moles
= 0.015 moles
B. a physical combination of two or more different materials.
According to the source below, the solubility of sulfanilamide in 95% ethyl alcohol at 78°C is 210 mg/mL. Since 0.1 g = 100 mg, we can set up a proportion:
(210 mg) / (1 mL) = (100 mg) / (x mL) Solving, x = 0.48 mL of 95% ethyl alcohol will be required.
I do not know previously the solubility of sulfanilamide in 95% ethyl alcohol. Let us accept the solubility you quoted here.
100/210 = 0.47619047619.. ≈ 0.48 (ml)
at 0C, the amount of sulfanilamide remains in the solution is: 14*(100/210) = 6.67 (mg), since you only have 0.48 ml solution.
The volume of the solution will change a little by cooling from 78C to 0C. You may also consider this volume change if you have data.
The correct answer:C) NaCl(s)
Hope this helps!
