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2 years ago

The half-life of 131I is 80 days. How much of a 500.0 mg sample remains after 3 half lives?

Chemistry

1 answer:

I am Lyosha [343]2 years ago

6 0

Answer:

62.5 mg

Explanation:

Just multiply the original amount by 1/2 three times:

500 mg x 1/2 x 1/2 x 1/2 = 62.5 mg

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When the forces acting on the object are balanced the object will?

Volgvan

Answer:

When two forces acting on an object are of similar size but acting in opposite directions, we say they are forces of balance. If the forces on an object are balanced (or if there are no forces acting on it), this is what happens: the object stays stationary

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3 years ago

The acid dissociation constant Ka of boric acid (H3BO3) is 5.8 times 10^-10. Calculate the pH of a 4.4 M solution of boric acid.

madam [21]

Answer: The pH of a 4.4 M solution of boric acid is 4.3

Explanation:

$H_3BO_3\rightarrow H^+H_2BO_3^-$

at t=0 cM 0 0

at eqm $c-c\alpha$ $c\alpha$ $c\alpha$

So dissociation constant will be:

$K_a=\frac{(c\alpha)^{2}}{c-c\alpha}$

Give c= 4.4 M and $\alpha$ = ?

$K_a=5.8\times 10^{-10}$

Putting in the values we get:

$5.8\times 10^{-10}=\frac{(4.4\times \alpha)^2}{(4.4-4.4\times \alpha)}$

$(\alpha)=0.000011$

$[H^+]=c\times \alpha$

$[H^+]=4.4\times 0.000011=4.8\times 10^{-5}M$

Also $pH=-log[H^+]$

$pH=-log[4.8\times 10^{-5}]=4.3$

Thus pH of a 4.4 M $H_3BO_3$ solution is 4.3

3 0

3 years ago

Baker’s Yeast is usually added to dough in baking products. It contains enzymes (catalysts) that are necessary for the rising do

STatiana [176]

Answer:

When I first began making bread, the science involved was always in the back of my mind. I had an idea of what occurred—my diagram for the chemical reactions

7 0

3 years ago

A 0.245-L flask contains 0.467 mol co2 at 159 °c. Calculate the pressure using the ideal gas law.

lubasha [3.4K]

Answer:

Pressure, P = 67.57 atm

Explanation:

Given the following data;

Volume = 0.245 L
Number of moles = 0.467 moles
Temperature = 159°C
Ideal gas constant, R = 0.08206 L·atm/mol·K

Conversion:

We would convert the value of the temperature in Celsius to Kelvin.

T = 273 + °C

T = 273 + 159

T = 432 Kelvin

To find the pressure of the gas, we would use the ideal gas law;

PV = nRT

Where;

P is the pressure.
V is the volume.
n is the number of moles of substance.
R is the ideal gas constant.
T is the temperature.

Making P the subject of formula, we have;

$P = \frac {nRT}{V}$

Substituting into the formula, we have;

$P = \frac {0.467*0.08206*432}{0.245}$

$P = \frac {16.5551}{0.245}$

Pressure, P = 67.57 atm

4 0

3 years ago

Convert 1.60 x 107 cm to mm in scientific notation please help

statuscvo [17]

Answer:

4.8x10^9

Explanation:

7 0

3 years ago