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Bond [772]
3 years ago
9

You have 40 g of a radioisotope. If the half-life of this radioisotope is 4 days, how many grams will remain after 12 days?

Chemistry
1 answer:
anygoal [31]3 years ago
5 0
With reference to radioactive material, half-life is the time required to 50% depletion of initial amount of material. 

Given: Initial amount of radioactive material = 40 g
Half life = 4 days.

Therefore, After 4 days, amount of compound left = 40/2 = 20 g
After 8 days, i.e 2 half-life, amount of compound left = 20/2 = 10 g
Finally after 12 days, i.e. 3 half-life, amount of compound left = 10/2 = 5 g

Thus, 5 <span>grams will remain after 12 days</span>
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1. A gas has a volume of 140L at 37 ºC and 620 kpa pressure. Calculate its volume at STP.
solniwko [45]

Answer:

1. Volume as STP = 755 L

2. Outside temperature = 255 K

3. Percentage yield = 70.5%

Explanation:

1. At STP, pressure  = 101.3 kpa, temperature  = 0°C or 273.15 K

Using the general gas equation :

P1V1/T1 = P2V2/T2

P1 = 620 kpa

V1 = 140 L

T1 = 37°C or (273.15 + 37) K = 310.15 K

P2 = 101.3 kpa

V2 = ?

T2 = 273.15 K

V2 = P1V1T2/P2T1

V2 = 620 × 140 × 273.15 / 101.3 × 310.15

V2 = 755 L

2. Using Charles' gas law:

V1/T1 = V2/T2

V1 = 2.5 L

T1 = 290 K

V2 = 2.2 L

T2 = ?

T2 = V2T1/VI

T2 = 2.2 × 290 / 2.5

T2 = 255 K

3. Equation of reaction : 2 Al + 3 CuSO4 ---> Al2 (SO4)3 + 3 Cu

From equation of the reaction,  2 moles of Al produces 3 moles of Cu

Molar mass of Al = 27 g; Molar mass of Cu = 63.5 g

2 moles of Al = 2 × 27 g = 54 g; 3 moles of Cu = 3× 63.5 = 190.5 g

54 g of Al produces 190.5 g of Cu

1.87 g of Al will produce 190.5/54 × 1.87 g of Cu = 6.60 g of Cu

Percentage yield = actual yield /theoretical yield × 100%

Percentage yield = 4.65/6.60 × 100%

Percentage yield = 70.5%

5 0
3 years ago
A metal stand specifies a maximum load of 450 lb. Will it support an aquarium that weighs 59.5 lb and is filled with 37.9 L of s
DedPeter [7]

First solve the mass of 37.9 L seawater

M = 37.9 L ( 1000 ml / 1L ) ( 1.03 g / ml)

M = 39037 g

Then convert it to lb

M = 39037 g ( 1 lb / 453.592 g)

M = 86.06 lb

<span>Total weight = 86.06 lb + 59.5 lb = 145.56 lb so it can support the aquarium</span>

5 0
3 years ago
What safety precautions are needed when running a brine electrolysis plant
nikdorinn [45]
Good ventilation as a product of it is pure Cl2  gas 
4 0
3 years ago
Calcium reacts with Hydrochloric acid to produce Calcium chloride and
hammer [34]

Answer:

Mass = 2.77 g

Explanation:

Given data:

Mass of HCl = 2 g

Mass of CaCl₂ produced = ?

Solution:

Chemical equation:

2HCl + Ca    →     CaCl₂ + H₂

Number of moles of HCl:

Number of moles = mass / molar mass

Number of moles = 2 g/ 36.5 g/mol

Number of moles = 0.05 mol

now we will compare the moles of HCl with CaCl₂.

                   HCl       :         CaCl₂

                     2         :          1

                   0.05     :       1/2×0.05 = 0.025 mol

Mass of CaCl₂:

Mass = number of moles × molar mass

Mass = 0.025 mol × 110.98 g/mol

Mass = 2.77 g

8 0
3 years ago
The amount of oxygen bound to hemoglobin _____.
Luba_88 [7]
The amount of oxygen bound to hemoglobin is 98.5% 
7 0
3 years ago
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