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Oliga [24]
3 years ago
10

How long will it take for a 750 mg sample of radium with a half life of 15 days to decay to exactly 68mg?

Chemistry
1 answer:
weqwewe [10]3 years ago
8 0

Answer:

52 da  

Step-by-step explanation:

Whenever a question asks you, "How long to reach a certain concentration?" or something similar, you must use the appropriate integrated rate law expression.

The i<em>ntegrated rate law for a first-order reaction </em>is  

ln([A₀]/[A] ) = kt

Data:

[A]₀ = 750 mg

 [A] =    68 mg

t_ ½ =   15 da

Step 1. Calculate the value of the rate constant.

 t_½ = ln2/k     Multiply each side by k

kt_½ = ln2         Divide each side by t_½

      k = ln2/t_½

         = ln2/15

         = 0.0462 da⁻¹

Step 2. Calculate the time

ln(750/68) = 0.0462t

         ln11.0 = 0.0462t

            2.40 = 0.0462t     Divide each side by 0.0462

                   t = 52 da

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Mars2501 [29]

Answer: 265.95 kelvins

Explanation:

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8 0
3 years ago
which of the following is the name given to the pairs of valence electrons that do not participate in bonding in diatomic oxygen
Bond [772]
The answer to your question is

D: Unshared Pair

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6 0
2 years ago
Studio
coldgirl [10]

Answer:

0.895 g/mL

Explanation:

Step 1: Given data

Mass of liquid Z (m): 2.763 lb

Volume of liquid Z (V): 5.93 cups

Step 2: Convert "m" to grams

We will use the relationship 1 lb = 453.59 g.

2.763 lb \times \frac{453.59 g}{1lb} = 1,253g

Step 3: Convert "V" to milliliters

We will use the relationship 1 cup = 236.59 mL.

5.93cup \times \frac{236.59mL}{1cup} = 1.40 \times 10^{3} mL

Step 4: Calculate the density of the liquid Z

The density (ρ) of the liquid Z is equal to its mass divided by its volume.

\rho = \frac{m}{V} = \frac{1,253g}{1.40 \times 10^{3}mL  } = 0.895 g/mL

4 0
3 years ago
How much force is required to accelerate an 8-kg wagon at a rate of 15 m/s
Dovator [93]

Answer:

<h2>120 N</h2>

Explanation:

The force acting on an object given it's mass and acceleration can be found by using the formula

force = mass × acceleration

From the question we have

force = 8 × 15

We have the final answer as

<h3>120 N</h3>

Hope this helps you

4 0
3 years ago
Hclo is a weak acid (ka=4.0x10^-8) and so the salt naclo acts as a weak base. what is the ph of a solution that is 0.037 m in na
ankoles [38]

<u>Given:</u>

Concentration of NaClO = 0.037 M

ka (HClO) = 4.0*10⁻⁸

<u>To determine:</u>

The pH of the NaClO solution

<u>Explanation:</u>

The hydrolysis of the weak base can be represented by the ICE table shown below-

                ClO-      +     H2O    ↔    HClO    +       OH-

Initial        0.037M                              0                    0

Change         -x                                 +x                  +x

Equilibrium  (0.037-x)                        x                     x

kb  = kw/ka =  [HClO][OH-]/[ClO-]

10⁻¹⁴/4*10⁻⁸ = x²/(0.037-x)

x = [OH-] = 9.62*10⁻⁵

p[OH-] = -log[OH-] = -log [9.62*10⁻⁵] = 4.02

pH = 14-p[OH-] = 14 - 4.02 = 9.98

Ans: pH of the solution is 9.98


7 0
3 years ago
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