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miss Akunina [59]
2 years ago
11

Round off the following numbers to the number of significant figures (sf) indicated.

Chemistry
2 answers:
barxatty [35]2 years ago
8 0

Explanation:

A. 7.52

B. 16.5

C. 85

D. 6.03

Flura [38]2 years ago
6 0

Answer:

a. 7.52

b. 16.5

c. 85

d. 6.03

Explanation:

significant number exempts 0 as a number which explains the last one. The two significant numbers there are 6 and 3

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What is the wavelength of an X-ray that has a frequency of 7.8 x 1017 Hz
SVEN [57.7K]

Answer:

λ = 0.38 ×10⁻⁹ m

Explanation:

Given data:

Wavelength of xray = ?

Frequency of xray = 7.8 ×10¹⁷ Hz

Solution:

Formula:

Speed of light = wavelength × frequency

speed of light = 3×10⁸ m/s

Now we will put the values in formula.

3×10⁸ m/s = λ × 7.8 ×10¹⁷ Hz

λ = 3×10⁸ m/s / 7.8 ×10¹⁷ Hz

         Hz = s⁻¹

λ = 3×10⁸ m/s / 7.8 ×10¹⁷s⁻¹

λ = 0.38 ×10⁻⁹ m

3 0
2 years ago
Water freezes at 0∘C and CO freezes at −205∘C. Which type of intermolecular force accounts for this difference in freezing point
Assoli18 [71]

Explanation:

The dipoles in CO are in opposite directions so they cancel each other out, although CO₂ has polar bonds, it is a nonpolar molecule. Therefore, the only intermolecular forces are London dispersion forces. Water (H2O) has hydrogen bond present which is a polar bond which has a high intermolecular force.

Water which has high intermolecular force will require more energy that is a higher temperature to overcome these attractions and are pulled together tightly to form a solid at higher temperatures, so their freezing point is higher.

As the temperature of a liquid decreases, the average kinetic energy of the molecules decreases and they move more slowly.

CO with lower intermolecular forces will not solidify until the temperature is lowered further.

6 0
3 years ago
Caffeine (C8H10N4O2) is a weak base with a pKb of 10.4. Calculate the pH of a solution containing a caffeine concentration of 41
RSB [31]

Answer:

pH → 7.47

Explanation:

Caffeine is a sort of amine, which is a weak base. Then, this pH should be higher than 7.

Caffeine + H₂O  ⇄  Caffeine⁺  +  OH⁻      Kb

1 mol of caffeine in water can give hydroxides and protonated caffeine.

We convert the concentration from mg/L to M

415 mg = 0.415 g

0.415 g / 194.19 g/mol = 2.14×10⁻³ mol

[Caffeine] = 2.14×10⁻³  M

Let's calculate pH. As we don't have Kb, we can obtain it from pKb.

- log Kb = pKb → 10^-pKb = Kb

10⁻¹⁰'⁴ = 3.98×10⁻¹¹

We go to equilibrium:

Caffeine + H₂O  ⇄  Caffeine⁺  +  OH⁻      Kb

Initially we have 2.14×10⁻³ moles of caffeine, so, after the equilibrium we may have (2.14×10⁻³ - x)

X will be the amount of protonated caffeine and OH⁻

     Caffeine     +    H₂O  ⇄  Caffeine⁺  +  OH⁻      Kb

   (2.14×10⁻³ - x)                         x                x

We make the expression for Kb:

3.98×10⁻¹¹ = x² / (2.14×10⁻³ - x)

We can missed the -x in denominator, because Kb it's a very small value.

So: 3.98×10⁻¹¹ = x² / 2.14×10⁻³

√(3.98×10⁻¹¹ . 2.14×10⁻³) = x → 2.92×10⁻⁷

That's the [OH⁻].  - log [OH⁻] = pOH

- log 2.92×10⁻⁷ = 6.53 → pOH

14 - pOH = pH → 14 - 6.53 = 7.47

4 0
3 years ago
What’s the difference between heterogeneous and homogeneous mixtures?
Ronch [10]

Answer:

Mixtures can be either homogeneous or heterogeneous. A mixture in which its constituents are distributed uniformly is called homogeneous mixture, such as salt in water. A mixture in which its constituents are not distributed uniformly is called heterogeneous mixture, such as sand in water.

5 0
2 years ago
Express 0.08010 in exponential notation to the proper significant figures
nataly862011 [7]
This would be 8.010 * 10^-2
3 0
3 years ago
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