1. Which of these statements is true?

For a sample of stomach acid that is 2.02×10−2 M in HCl, how many moles of HCl are in 14.6 mL of the stomach acid?

GaryK [48]

Answer:

0.0002949 moles

Explanation:

Concentration = 2.02×10−2 M

Volume = 14.6 mL = 0.0146 L (Upon converting to litres)

Number of moles = ?

These variables are related by the fllowing equation;

Concentration = Number of moles / Volume

Number of moles = Concentration * Volume

Number of moles = 2.02×10−2 * 0.0146 = 0.0002949 moles

8 0

3 years ago

A 60.0 mL solution of 0.112 M sulfurous acid (H2SO3) is titrated with 0.112 M NaOH. The pKa values of sulfurous acid are 1.857 (

djverab [1.8K]

Answer:

a)4.51

b) 9.96

Explanation:

Given:

NaOH = 0.112M

H2S03 = 0.112 M

V = 60 ml

H2S03 pKa1= 1.857

pKa2 = 7.172

a) to calculate pH at first equivalence point, we calculate the pH between pKa1 and pKa2 as it is in between.

Therefore, the half points will also be the middle point.

Solving, we have:

pH = (½)* pKa1 + pKa2

pH = (½) * (1.857 + 7.172)

= 4.51

Thus, pH at first equivalence point is 4.51

b) pH at second equivalence point:

We already know there is a presence of SO3-2, and it ionizes to form

SO3-2 + H2O <>HSO3- + OH-

$Kb = \frac{[ HSO3-][0H-]}{SO3-2}$

$Kb = \frac{10^-^1^4}{10^-^7^.^1^7^2} = 1.49*10^-^7$

[HSO3-] = x = [OH-]

mmol of SO3-2 = MV

= 0.112 * 60 = 6.72

We need to find the V of NaOh,

V of NaOh = (2 * mmol)/M

= (2 * 6.72)/0.122

= 120ml

For total V in equivalence point, we have:

60ml + 120ml = 180ml

[S03-2] = 6.72/120

= 0.056 M

Substituting for values gotten in the equation $Kb=\frac{[HSO3-][OH-]}{[SO3-2]}$

We noe have:

$1.485*10^-^7=\frac{x*x}{(0.056-x)}$

$x = [OH-] = 9.11*10^-^5$

$pOH = -log(OH) = -log(9.11*10^-^5)$

=4.04

pH = 14- pOH

= 14 - 4.04

= 9.96

The pH at second equivalence point is 9.96

4 0

3 years ago

Water exhibits a type of magnetism called ___________________ whereby in the presence of a strong magnetic field, the normally n

Lilit [14]

The answer is diamagnetism. It is a significant mechanical effect that happens in all materials; when it is the only influence to the magnetism, the material is named diamagnetic. Quartz and water are samples of diamagnetic materials. The diamagnetic influence is usually unimportant in materials holding strong lasting magnetic moments.

5 0

4 years ago

1) How many atoms are in 0.54 moles of Cu? show work

mario62 [17]

<h3>Answer:</h3>

3.3 × 10²³ atoms Cu

<h3>General Formulas and Concepts:</h3>

<u>Pre-Algebra</u>

Order of Operations: BPEMDAS

Brackets
Parenthesis
Exponents
Multiplication
Division
Addition
Subtraction

Left to Right<u> </u>

<u>Chemistry</u>

<u>Atomic Structure</u>

Moles
Avogadro's Number - 6.022 × 10²³ atoms, molecules, formula units, etc.

<u>Stoichiometry</u>

Using Dimensional Analysis

<h3>Explanation:</h3>

<u>Step 1: Define</u>

[Given] 0.54 moles Cu

[Solve] atoms Cu

<u>Step 2: Identify Conversions</u>

Avogadro's Number

<u>Step 3: Convert</u>

[DA] Set up: $\displaystyle 0.54 \ mol \ Cu(\frac{6.022 \cdot 10^{23} \ atoms \ Cu}{1 \ mol \ Cu})$
[DA] Multiply [Cancel out units]: $\displaystyle 3.25188 \cdot 10^{23} \ atoms \ Cu$

<u>Step 4: Check</u>

<em>Follow sig fig rules and round. We are given 2 sig figs.</em>

3.25188 × 10²³ atoms Cu ≈ 3.3 × 10²³ atoms Cu

7 0

3 years ago

[1] b) In a local election there were 8000 registered voters. Of these 3200 voted. What was the percentage that voted? [1] <

Alexandra [31]

Answer:

40% of registered voters voted

Explanation:

3200 out of 8000,

or :

3200 / 8000

= 0.4

0.4 x 100 = 40

40% of registered voters voted

4 0

2 years ago