Question

Problem 16.45 - Enhanced - with Feedback You may want to reference (Pages 679 - bou) Section 16.5 wnile completing this problem. Part A Calculate [OH-] for 2.0 x 10-'M Sr(OH), Express your answer using two significant figures. O A ROO? [OH-] = M Submit Request Answer Part B Complete previous part(s) Part Calculate (OH) for 2.090 g of LiOH in 220.0 mL of solution Express your answer using four significant figures. ALO * ROO? [OH-] = M Submit Request Answer

Answer 1

A)
1 Sr(OH)2 has 2 OH- ions

So,
[OH-] = 2*[Sr(OH)2]
=2*2.0*10^-3 M
= 4.0*10^-3 M

Answer: 4.0*10^-3 M

B)

Molar mass of LiOH,
MM = 1*MM(Li) + 1*MM(O) + 1*MM(H)
= 1*6.968 + 1*16.0 + 1*1.008
= 23.976 g/mol


mass(LiOH)= 2.090 g

use:
number of mol of LiOH,
n = mass of LiOH/molar mass of LiOH
=(2.09 g)/(23.98 g/mol)
= 8.717*10^-2 mol
volume , V = 2.2*10^2 mL
= 0.22 L


use:
Molarity,
M = number of mol / volume in L
= 8.717*10^-2/0.22
= 0.3962 M

So,
[OH-] = 0.3962 M
Answer: 0.3962 M