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3 years ago

You have 400 kg of a radioactive substance with a short half-life of 1000 years. how much will be left after these times?

1 answer:

8 0

Half-life of a radioactive substance is the time required to reduce the amount of substance to half of its initial amount.

In present case, half-life is material is given as 1000 years and initial amount of material is given as 400 kg

Answer 1) Since, half-life of radio-active substance is 1000 years, therefore after 1st half life, amount of the material will be left to half the initial amount. Hence, amount of substance left after 1000 years = 400/2 = 200 kg.

Answer 2) For 2000 years, radioactive material has crossed 2 times the half life. Therefore , amount of the material will be left to 1/4 the initial amount. Hence, amount of substance left after 2000 years = 400/4 = 100 kg.

Answer 3) For 4000 years, radioactive material has crossed 4 times the half life. Therefore , amount of the material will be left to 1/16 the initial amount. Hence, amount of substance left after 4000 years = 400/16 = 25 kg.

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calcualte pressure at STP in 10.0 L vessel after reaction of 1.0 L hydrochloride acid (concentration 35% and density 1.28 g/cub.

sattari [20]

Answer:

The pressure in the vessel is 13,3 atm.

Explanation:

The reaction that occurs in vessel (where limestone is 96% of CaCO₃) is:

2 HCl (aq)+ CaCO₃ (s) → CaCl₂(aq)+ H₂O(l)+ CO₂(g)

The increase in the pressure of the vessel after the reaction is by formation of a gas (CO₂). So we have to find the produced moles of this gas and apply the gas ideal law to find the pressure.

We have to find the limit reactant, to do so, we have to calculate the moles of each reactant in the reaction, the one that have the less moles will be the limit reactant:

HCl:

1,0L × (35/100) × (1000 cm³/1L) × (1,28 g/ 1cm³) × (1mol HCl/ 36,46 g) ÷ 2mol

(Concentration) (L to cm³) (cm³ to g) (g to mol) (moles of reaction)

moles of HCl= 6,14 mol

CaCo₃:

1,0 kg × (96/100) × (1000 g/1kg) × (1 mol/100,09g)

(Limestone) (CaCo₃ in limestone) (kg to g) (g to mol)

moles of CaCo₃= 9,59 mol

So, <em>reactant limit is HCl</em>

This reaction have a yield of 97%. So, the CO₂ moles are:

6,14 mol × 97÷ = 5,96 mol CO₂

The ideal gas formula to obtain pressure is:

P = nRT/V

Where: n = 5,96mol; R= 0,082 atm×L/mol×K; T = 273,15 (until STP conditions) and V= 10,0 L

Replacing this values in the equation the pressure is

P = 13,3 atm

I hope it helps!

7 0

3 years ago

How is dry ice different from ordinary ice?

True [87]

Answer: Well "ordinary ice" is made from water (as we all know) and dried ice is made from carbon dioxide gas

Explanation:

•Hope this helps•

5 0

3 years ago

When 231. mg of a certain molecular compound X are dissolved in 65. g of benzene (CH), the freezing point of the solution is mea

Elan Coil [88]

Answer:

Molar mass X = 18.2 g/mol

Explanation:

Step 1: Data given

Mass of compound X = 231 mg = 0.231 grams

Mass of benzene = 65.0 grams

The freezing point of the solution is measured to be 4.5 °C.

Freezing point of pure benzene = 5.5 °C

The freezing point constant for benzene is 5.12 °C/m

Step 2: Calculate molality

ΔT = i*Kf*m

⇒ΔT = the freezing point depression = 5.5 °C - 4.5 °C = 1.0 °C

⇒i = the Van't hoff factor = 1

⇒Kf = the freezing point depression constant for benzene = 5.12 °C/m

⇒m = the molality = moles X / mass benzene

m = 1.0 / 5.12 °C/m

m = 0.1953 molal

Step 3: Calculate moles X

Moles X = molality * mass benzene

Moles X = 0.1953 molal * 0.065 kg

Moles X = 0.0127 moles

Step 4: Calculate molar mass X

Molar mass X = mass / moles

Molar mass X = 0.231 grams / 0.0127 moles

Molar mass X = 18.2 g/mol

5 0

3 years ago

How many valence electrons does the Lewis structure for a chlorine atom show

ohaa [14]

Answer: D

Explanation:

Chlorine is in group 7 or (VII) in Roman numerals, which means it has 7 balance electrons. It only needs one electron to become stable, hence it is next to the noble gases

6 0

3 years ago

Read 2 more answers

How does mixture relate to life

masya89 [10]

Answer:

For example, when we bake a cake, it's a result of a mixture of eggs, flour, sugar, and other ingredients. Any time two or more items are combined, a mixture is formed. Sometimes, the different parts of a mixture can be separated into individual entities. Other times, they're married for as long as they exist.

Explanation:

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3 years ago