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3 years ago

Substance in which two or more elements are combined in a fixed proportion

Chemistry

1 answer:

Firdavs [7]3 years ago

8 0

Answer: compound

Explanation:

Element is a pure substance which is composed of atoms of similar elements.It can not be decomposed into simpler constituents using chemical reactions.Example: Copper $Cu$

Compound is a pure substance which is made from atoms of different elements combined together in a fixed ratio by mass.It can be decomposed into simpler constituents using chemical reactions. Example: water $H_2O$

Mixture is a substance which has two or more components which do not combine chemically and do not have any fixed ratio in which they are present. Example: Air

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Carbon-14 is a radioactive isotope that decays according to first-order kinetics in a process that has a half-life of 5730 years

Sliva [168]

Answer : The time passed in years is $2.83\times 10^3\text{ years}$

Explanation :

Half-life = 5730 years

First we have to calculate the rate constant, we use the formula :

$k=\frac{0.693}{t_{1/2}}$

$k=\frac{0.693}{5730\text{ years}}$

$k=1.21\times 10^{-4}\text{ years}^{-1}$

Now we have to calculate the time passed.

Expression for rate law for first order kinetics is given by:

$t=\frac{2.303}{k}\log\frac{a}{a-x}$

where,

k = rate constant = $1.21\times 10^{-4}\text{ years}^{-1}$

t = time passed by the sample = ?

a = let initial amount of the reactant = X g

a - x = amount left after decay process = $71\% \times (x)=\frac{71}{100}\times (X)=0.71Xg$

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

$t=\frac{2.303}{1.21\times 10^{-4}}\log\frac{X}{0.71X}$

$t=2831.00\text{ years}=2.83\times 10^3\text{ years}$

Therefore, the time passed in years is $2.83\times 10^3\text{ years}$

8 0

3 years ago

Which indicator will be the same color in hydrochloric acid as it is in pure water?

djverab [1.8K]

Phenolphthalein
In acid it is colourless and in water also colourless

3 0

3 years ago

What are the advantages and disadvantages of fission?

viktelen [127]

<u>Advantages of Nuclear Fission</u>

Nuclear fission provides cheapest energy . Almost 10% of electricity used in the world is obtained from the fission reaction

It offers a low-emission energy solution since there is no carbon dioxide gas emitted during the nuclear fission reaction

A well controlled and maintained nuclear reactor can produce energy for 36 to 40 months so works for .

It is a reliable source of energy as energy is obtained from uranium which is available is plenty.

It provides very concentrations of energy as it can provide large amount of energy from small amount of fuel.

The reaction gives less annual mortality rate of any energy resource with 90 deaths per trillion kilowatt hours

<u>Disadvantages of Nuclear Fission </u>

It is dangerous and also explosive.

It creates harmful and radioactive waste products.

It is not a renewable energy resource like solar and wind energy

It can develop long-term health issues for people exposed to then radioactive waves.

It involves high cost in installation of the reactors.

5 0

3 years ago

If 24.6 grams of lithium react with excess water, how many liters of hydrogen gas can be produced at 301 Kelvin and 1.01 atmosph

andreev551 [17]

Answer: 43.3 l

Explanation:

1) Chemical equation:
2 Li(s) + 2 H₂O (l) → 2LiOH(aq) + H₂ (g)

2) Mole ratios:

2 mol Li : 2 mol H₂O : 2 mol LiOH : 1 mol H₂

3) Number of moles of Li that react

n = mass in grams / atomic mass = 24.6g / 6.941 g/mol = 3.54 moles

4) Yield

Proportion:

2 mol Li / 1 mol H₂ = 3.54 mol Li/ x

⇒ x = 3.54 mol Li × 1 mol H / 2 mol Li = 1.77 mol H₂

4) Ideal gas equation

PV = nRT ⇒ V = nRT / P

V = 1.77 mol × 0.0821 [atm×l / (mol×K)] × 301 K / 1.01 atm = 43.3 l

V = 43.3 l ← answer

7 0

3 years ago

What is the percent composition of hydrogen in water

pshichka [43]

Answer:

11.19% hydrogen and 88.81% oxygen

Explanation:

6 0

3 years ago