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2 years ago

Why do you think elements must be heated before they emit colored light?

1 answer:

4 0

The colored light emitted is energy and in order to emit energy the element should first obtain energy. The energy absorbed by the substance can be in the form of radiation, heat or electricity. Hope this answers the question. Have a nice day.

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Carbon-14 has a half-life of 5720 years and this is a first order reaction. If a piece of wood has converted 75% of the carbon-1

liraira [26]

Answer: 1145.8 years

Explanation:

Half-life of carbon-14 = 5720 years

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

$k=\frac{0.693}{5720\text{years}}$

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

Now we have to calculate the age of the sample:

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 = age of sample = ?

a = let initial amount of the reactant = 100 g

x = amount decayed = 75 g

a - x = amount left after decay process = 100 - 75 = 25g

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

$t==\frac{2.303}{1.21\times 10^{-4}}\log\frac{100}{25}$

$t=1145.8years$

8 0

3 years ago

Read 2 more answers

2. In which state of matter do particles vibrate in place? *

Mariana [72]

solid.................

5 0

2 years ago

Read 2 more answers

Enter a balanced nuclear equation for the production of lead-212, used in the treatment of some cancers, from the beta decay of

MariettaO [177]

Answer:

$\frac{212}{81}Tl ------>\beta + \frac{212}{82}Pb$

Explanation:

Beta emission involves the conversion of a neutron to a proton, an electron and a neutrino. This leads to a reduction in the neutron-proton ratio.

During a beta emission, the mass number of the parent and daughter nuclei remain the same. The atomic number of the daughter nucleus increases by one unit above that of the parent nucleus as we can see from the equation.

Hence, the daughter nucleus is found one place after its parent in the periodic table.

8 0

2 years ago

Which of the following elements has the lowest electronegativity?

just olya [345]

A) K is the element with the lowest electronegativity

7 0

3 years ago

An organic compound is 61.5% C, 2.56% H and 35.9% N by mass. 2.00 grams of this gas is entered into a 300.0 mL flask and heated

pashok25 [27]

Answer:

C₄H₂N₂

Explanation:

First we calculate the moles of the gas, using PV=nRT:

P = 2670 torr ⇒ 2670/760 = 3.51 atm

V = 300 mL ⇒ 300/1000 = 0.3 L

T = 228 °C ⇒ 228 + 273.16 = 501.16 K

3.51 atm * 0.3 L = n * 0.082atm·L·mol⁻¹·K⁻¹ * 501.16 K

n = 0.0256 mol

Now we calculate the molar mass of the compound:

2.00 g / 0.0256 mol = 78 g/mol

Finally we use the percentages given to calculate the empirical formula:

C ⇒ 78 g/mol * 61.5/100 ÷ 12g/mol = 4

H ⇒ 78 g/mol * 2.56/100 ÷ 1g/mol = 2

N ⇒ 78 g/mol * 35.9/100 ÷ 14g/mol = 2

So the empirical formula is C₄H₂N₂

6 0

3 years ago