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sveticcg [70]
3 years ago
12

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
2 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
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