Ask Me Help Desk - NaOH in milk of magnesia

NaOH in milk of magnesia

. NaOH, lye, is a strong base. Concentrated sodium hydroxide
Is extremely dangerous if ingested. Mg(OH)2 is also
A strong base. However, it is safely consumed as "milk of
magnesia" by millions daily. Why?

a. It is not the above statement is false.
b. Excess hydroxide is consumed as hydrogen gas.
c. The low solubility of Mg(OH)2 in water assures the hydroxide
Concentration remains low.
d. The high solubility of Mg(OH)2 in water assures the magnesium
Hydroxide does not dissociate into hydroxide ions.

Volume of HBr gas

What is the volume (in L) of 15.0 g of HBr gas at 715 torr and
90.0 oC? (hint: calculate the number of moles of HBr first).

a. 13.0 b. 6.51
c. 9.79 d. 5.88
e. none of the above.

gas in a cyllinder

16. The gas in a cylinder at 20.0 oC exerts a pressure of 200 atm. The cylinder is
heated to a temperature of 200 oC. To what value will the pressure rise assuming
the cylinder volume does not change?

a. 484 atm. b. 223 atm. c. 2000 atm. d. 20 atm.
e. none of the above.

pressure correspondence

Which pressure does not correspond to 1.25 atm? ( 1 in. = 2.54 cm)?

a. 950 torr b. 950 cm Hg
c. 37.4 in. Hg d. all of the above.
e. none of the above

POH of ph 3.20

A solution is found to have a pH 3.20. What is its pOH?

a. 5.80 b. 6.80
c. 14.00 d. 10.80

Changing tem of hydrogen gas at constant pressure will.

Changing the temperature of 4.0 mol of hydrogen gas at
Constant pressure from 100 oC to 200 K will

a. increase its mass by a factor of three.
b. decrease the volume that the gas occupies.
c. increase the kinetic energy of the hydrogen molecules.
d. decrease the density by a factor of two.

How many moles

In one experiment, a dry sample of an unknown
Gas was collected. Its volume at 745 mm Hg and
63.0 oC was 815.5 mL. How many moles of this gas
Was obtained?

a. 0.0290 moles b. 2.90 moles
c. 29.0 moles d. 2310 moles
e. none of the above.

Thank you for taking the time to copy your homework to AMHD.
Please refer to this announcement: Ask Me Help Desk - Announcements in Forum : Homework Help

I appreciate your response and undersand why you would think this. However this is NOT MY HOMEWORK just copied and pasted. THIS IS FROM A STUDY GUIDE and we ALREADY took THE EXAM AND FINISHED THE COURSE. I am looking to UNDERSTAND WHY I got the questions from my test WRONG. Those are the questions I posted.

I would GREATLY appreciate anyone's input. I am TRYING TO LEARN form my EXAM!

Quote:

Originally Posted by WhitneyRobinson

. NaOH, lye, is a strong base. Concentrated sodium hydroxide
is extremely dangerous if ingested. Mg(OH)2 is also
a strong base. However, it is safely consumed as "milk of
magnesia" by millions daily. Why?

a. It is not the above statement is false.
b. Excess hydroxide is consumed as hydrogen gas.
c. The low solubility of Mg(OH)2 in water assures the hydroxide
concentration remains low.
d. The high solubility of Mg(OH)2 in water assures the magnesium
hydroxide does not dissociate into hydroxide ions.

c) Mg(OH)2 is not very soluble in water. The hydroxide concentration remains very low.

Quote:

pOH of ph 3.20
A solution is found to have a pH 3.20. What is its pOH?

a. 5.80 b. 6.80
c. 14.00 d. 10.80

Isn't that 14 - 3.20, giving 10.8? Well, I'm not sure of that...

Quote:

changing tem of hydrogen gas at constant pressure will.
Changing the temperature of 4.0 mol of hydrogen gas at
constant pressure from 100 oC to 200 K will

a. increase its mass by a factor of three.
b. decrease the volume that the gas occupies.
c. increase the kinetic energy of the hydrogen molecules.
d. decrease the density by a factor of two.

a. is not the answer since mass is always constant for a fixed number of moles.
b. that can be the good answer since 200K is -73 C, thus cooling
c. no since this involves cooling, there's a decrease in kinetic energy
d. no, the volume decreases for a fixed mass, the density increases.

Quote:

gas in a cyllinder
16. The gas in a cylinder at 20.0 oC exerts a pressure of 200 atm. The cylinder is
heated to a temperature of 200 oC. To what value will the pressure rise assuming
the cylinder volume does not change?

a. 484 atm. b. 223 atm. c. 2000 atm. d. 20 atm.
e. none of the above.

Use

$\frac{P_1V_1}{T_1} = \frac{P_2V_2}{T_2}$ ,

V constant, so

$\frac{P_1}{T_1} = \frac{P_2}{T_2}$

Quote:

What is the volume (in L) of 15.0 g of HBr gas at 715 torr and
90.0 oC? (hint: calculate the number of moles of HBr first).

a. 13.0 b. 6.51
c. 9.79 d. 5.88
e. none of the above.

$15.0\,g\,HBr \div 80.91 \,g/mol = 0.1854\, moles$

The temperature is 90.0 C = 363.15 Kelvin (always use Kelvin in pressure-volume calculations)

ideal gas law:

$PV=nRT$

R = 62.363 67(11) L Torr K−1 mol−1 (from Gas constant - Wikipedia, the free encyclopedia. Note I selected this one for its units.)

$715 \times V = 0.1854 \times 62.36367 \times 363.15=4198.82$

V=5.87 Liters. This is close enough to "d" that I'd select that one.

Quote:

16. The gas in a cylinder at 20.0 oC exerts a pressure of 200 atm. The cylinder is
heated to a temperature of 200 oC. To what value will the pressure rise assuming
the cylinder volume does not change?

a. 484 atm. b. 223 atm. c. 2000 atm. d. 20 atm. e. none of the above.

T1 = 20 C (293.15 K).
P1 = 200 atm
V is constant
T2 = 200 C (473.15 K)

$\frac {P_1V_1}{T_1}=\frac {P_2V_2}{T_2}$

Since V1 = V2,

$\frac {200}{298.15}=\frac {P_2}{473.15}$

$P_2 = 317.39\, atm$

Looks like the answer is "e"

$pOH = -log([OH^-])$

where [OH^-] is the hydroxide ion concentration. It's analogous to pH.

Quote:

A solution is found to have a pH 3.20. What is its pOH?

a. 5.80 b. 6.80
c. 14.00 d. 10.80

$[H^+] + [OH^-] = 10^{14}$

or

$pH + pOH = 14$

14 - 3.2 = 10.8

So, Unknown008 got that right.