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timama [110]
3 years ago
11

How do scientists measure the idea of time so long ago?

Chemistry
1 answer:
aleksklad [387]3 years ago
4 0

The Ancient Egyptians used simple sundials and divided days into smaller parts, and it has been suggested that as early as 1,500BC, they divided the interval between sunrise and sunset into 12 parts. ... Known as a clepsydra, it uses a flow of water to measure time.

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Draw the alkane formed when 4,5,5-trimethyl-1-hexyne is treated with two equivalents of hbr.
AveGali [126]
<h3>Answer:</h3>

             The Alkane formed is 5,5-dibromo-2,2,3-trimethylhexane. as shown below in attached scheme (Green Color).

<h3>Explanation:</h3>

                        Alkynes like Alkenes undergo <em>Electrophillic Addition Reactions</em>. The reaction given is a two step reaction. In step 1, the Alkyne adds first equivalent of HBr obeying <em>Markovnikov's rule</em> (i.e. Bromine will add to carbon containing less number of hydrogen atoms) and forms <em>2-bromo-4,5,5-trimethylhex-1-ene</em>. In step 2, the alkene formed in first step (2-bromo-4,5,5-trimethylhex-1-ene) undergoes addition reaction with the second equivalent of HBr via Markovnikov's rule to produce <em>5,5-dibromo-2,2,3-trimethylhexane</em>.

The scheme is attached below, Blue color is assigned to starting Alkyne, Red color is assigned to intermediate Alkene and Green color is assigned to product Alkane respectively.

3 0
4 years ago
Read 2 more answers
Elena held a rock weighing 1 N in her hand. The rock has no velocity. <br> KE________?
nignag [31]

KE = 0

<h3>Further explanation  </h3>

Energy is the ability to do work  

Energy because its motion is expressed as Kinetic energy (KE) which can be formulated as:  

\large{\boxed{\bold{KE=\frac{1}{2}mv^2}}}

So for two objects that have the same speed, the greater the mass of the object, the greater the kinetic energy  

The stone in hand is in a motionless state (at rest) so that its velocity (v) = 0, so it has no kinetic energy

But this stone can have <em>potential energy that is gained due to its height</em>

5 0
3 years ago
With reference to He-4 (or the diagram), explain the term isotopes.
boyakko [2]

Answer:

Isotopes are basically atoms of an element that have an unequal number of neutrons and protons. Of course the proton number remains the same, but the neutron number either decreases or increases, which leads to an overall change in mass. However, no chemical properties of the atom/element are changed as the electrons are the same number and do not react. In regards to Helium 4, the original number of neutrons in Helium is 2, and protons 2 as well. We see an equal number of neutrons and protons, hence an unchanged mass, and the element is <em>not</em> an isotope.

6 0
3 years ago
Suppose it took 108 joules of energy to raise a bar of gold from 25 °C to 29.7°C. Given that the specific heat capacity of gold
Lady bird [3.3K]

Answer:

m = 180 g

Explanation:

Given data:

Energy absorbed = 108 J

Mas of gold = ?

Initial temperature = 25°C

Final temperature = 29.7 °C

Specific heat capacity of gold = 0.128 J/g.°C

Solution:

Formula:

Q = m.c. ΔT

Q = amount of heat absorbed or released

m = mass of given substance

c = specific heat capacity of substance

ΔT = change in temperature

ΔT =29.7 °C - 25°C

ΔT = 4.7 °C

108 J = m ×0.128 J/g.°C ×4.7 °C

108 J = m ×0.60 J/g

m = 108 J/0.60 J/g

m = 180 g

3 0
3 years ago
potassium, k, has an atomic number of 19 and an atomic mass of 39 how many electrons does a neutral atom of K have?
coldgirl [10]
A neutral atom of potassium has 19 electrons.
8 0
3 years ago
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