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cluponka [151]
4 years ago
6

At a certain temperature, the ph of a neutral solution is 7.43. what is the value of kw at that temperature? express your answer

numerically using two significant figures.
Chemistry
1 answer:
Delvig [45]4 years ago
7 0

The formula for Kw is:

Kw= [H]*[OH]

where [H] and [OH] are concentrations 

We are given the pH so we can calculate the [H] concentration from the formula:
pH=-log[H] 
7.43 = -log[H]

[H] = 3.715x10^-8 M

In neutral solution, [H] = [OH], therefore: 

<span>[OH]= 3.715x10^-8 M

Calculating Kw:

Kw = (3.715x10^-8)*( 3.715x10^-8)</span>

<span>Kw = 1.38 x 10^-15 </span>

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How many molecules are in 7.62 L of CH4, at 87.5°C and 722 torr
pickupchik [31]

Answer: There are 1.469 \times 10^{23} molecules present in 7.62 L of CH_4 at 87.5^{o}C and 722 torr.

Explanation:

Given : Volume = 7.62 L

Temperature = 87.5^{o}C = (87.5 + 273) K = 360.5 K

Pressure = 722 torr

1 torr = 0.00131579

Converting torr into atm as follows.

722 torr = 722 torr \times \frac{0.00131579 atm}{1 torr}\\= 0.95 atm

Therefore, using the ideal gas equation the number of moles are calculated as follows.

PV = nRT

where,

P = pressure

V = volume

n = number of moles

R = gas constant = 0.0821 L atm/mol K

T = temperature

Substitute the values into above formula as follows.

PV = nRT\\0.95 atm \times 7.62 L = n \times 0.0821 L atm/mol K \times 360.5 K\\n = \frac{0.95 atm \times 7.62 L}{0.0821 L atm/mol K \times 360.5 K}\\= \frac{7.239}{29.59705}\\= 0.244 mol

According to the mole concept, 1 mole of every substance contains 6.022 \times 10^{23} atoms. Hence, number of atoms or molecules present in 0.244 mol are calculated as follows.

0.244 mol \times 6.022 \times 10^{23}\\= 1.469 \times 10^{23}

Thus, we can conclude that there are 1.469 \times 10^{23} molecules present in 7.62 L of CH_4 at 87.5^{o}C and 722 torr.

5 0
3 years ago
63 C = _____ 63 K 336 K 210 K 163 K
swat32
T K = ºC + 273

T = 63 + 273

T = 336 K

hope this helps!

4 0
4 years ago
Read 2 more answers
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