Answer:
3.46 x 10²⁴ molecules.
Explanation:
- <em>Knowing that every one mole of a substance contains Avogadro's no. of molecules (NA = 6.022 x 10²³).</em>
<em><u>Using cross multiplication:</u></em>
1.0 mole of HBr → 6.022 x 10²³ molecules.
5.75 mole of HBr → ??? molecules.
∴ The no. of molecules of HBr are in 5.75 mol = (6.022 x 10²³ molecules) ( 5.75 mole) / (1.0 mol) = 3.46 x 10²⁴ molecules.
Explanation:
Ammonium Fluoride and Potassium Sulphate
Given the length of each side of a cube and its mass, the density can be obtained which can then help identify the type of material it's made of. This is because density is a unique and intrinsic property of materials. For this problem, the density is determined to be 10g/cm^3. Looking at a table of densities, the metal is most likely actinium, which has an exact density of 10 g/cm^3.
Answer:
pH = 12.43
Explanation:
<em>...is titrating 212.7 mL of a 0.6800 M solution of hydrazoic acid (HN3) with a 0.2900 M solution of KOH. The p Ka of hydrazoic acid is 4.72. Calculate the pH of the acid solution after the chemist has added 571.6 mL of the KOH solution to it</em>.
To solve this question we need to know that hidrazoic acid reacts with KOH as follows:
HN3 + KOH → KN3 + H2O
<em>Moles KOH:</em>
0.5716L * (0.2900mol /L) =0.1658 moles of KOH
<em>Moles HN3:</em>
0.2127L * (0.6800mol/L) = 0.1446 moles HN3
As the reaction is 1:1, the KOH is in excess. The moles in excess of KOH are:
0.1658 moles - 0.1446 moles =
0.0212 mol KOH
In 212.7mL + 571.6mL = 784.3mL = 0.7843L
The molarity of KOH = [OH-] is:
0.0212 mol KOH / 0.7843L = 0.027M = [OH-]
The pOH is defined as -log [OH-]
pOH = -log 0.027M
pOH = 1.57
pH = 14 - pOH
pH = 12.43