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Zinaida [17]
3 years ago
9

A radioisotope has a half-life of 12 days. If a sample is measured to contain 5 grams of radioisotope, how much time has passed

if the sample originally measured 160 grams of radioisotope?​
Chemistry
1 answer:
Sophie [7]3 years ago
7 0
60 days have passed. In every 12 days the radioisotope loses half of its life. So in the first 12 days, from 160 grams it decreases to half so it becomes 80 grams. The second 12 days, from 80 grams, it decreases to half and becomes 40 g. The third 12 days, from 40 it becomes half to 20 g. The fourth 12 days, from 20 g it becomes half to 10 g. And in the fifth 12 days, from 10 g it becomes half to 5 grams. So 5 times it became half.
5 x 12 ( days)= 60 days
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How many molecules are in 1kg of water
Mila [183]

Answer:

334.2× 10²³ molecules

Explanation:

Given data:

Mass of water = 1 Kg ( 1000 g )

Number of molecules = ?

Solution:

Number of moles of water:

Number of moles = mass/ molar mass

Number of moles = 1000 g/ 18 g/mol

Number of moles = 55.5 mol

1 mole contain 6.022× 10²³ molecules

55.5 mol×6.022× 10²³ molecules

334.2× 10²³ molecules

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How many seconds are there in 23 days ?
Brrunno [24]
Since there are 23 days and 24 hours in each day, you multi-ply them and get 552 hours. Since each hours is 60 minutes, 552*60 is 33120 minutes. Since one minute is 60 seconds, 60*33120 is 1,987,200 seconds. Therefore, there are 1,987,200 seconds in 23 days. 
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The rate constant for the second-order reaction: 2NOBr(g) → 2NO(g) + Br2(g) is 0.80/(M · s) at 10°C. Starting with a concentrati
a_sh-v [17]

Answer : The concentration of NOBr after 95 s is, 0.013 M

Explanation :

The integrated rate law equation for second order reaction follows:

k=\frac{1}{t}\left (\frac{1}{[A]}-\frac{1}{[A]_o}\right)

where,

k = rate constant = 0.80M^{-1}s^{-1}

t = time taken  = 95 s

[A] = concentration of substance after time 't' = ?

[A]_o = Initial concentration = 0.86 M

Now put all the given values in above equation, we get:

0.80=\frac{1}{95}\left (\frac{1}{[A]}-\frac{1}{(0.86)}\right)

[A] = 0.013 M

Hence, the concentration of NOBr after 95 s is, 0.013 M

4 0
2 years ago
A student states that an exothermic chemical reaction can transfer its heat only by convection and conduction. Which disproves t
Over [174]
b is the right answer

6 0
3 years ago
Read 2 more answers
Determine the empirical formula of a
k0ka [10]

Answer:

AuCl

Explanation:

Given parameters:

Mass of Gold  = 2.6444g

Mass of Chlorine  = 0.476g

Unknown:

Empirical formula  = ?

Solution:

Empirical formula is the simplest formula of a compound. Here is the way of determining this formula.

Elements                                     Au                                             Cl

Mass                                         2.6444                                     0.476

Molar mass                                 197                                          35.5

Number of moles                  2.6444/197                                 0.476/35.5

                                                 0.013                                           0.013

Divide by the

smallest                                 0.013/0.013                                 0.013/0.013

                                                       1                                                   1

The empirical formula of the compound is AuCl

3 0
2 years ago
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