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3 years ago

I’m having hard time to understand can someone answer it and explain it

Chemistry

1 answer:

tekilochka [14]3 years ago

7 0

Number #2 is joule

In the SI system the unit of heat is the joule. The calorie was defined so that the heat capacity of water was equal to one.The heat capacity of a substance is the amount of heat required to raise the temperature of a defined amount of pure substances by one degree.

Number #3 is Endothermic

Why? I can't explain. I Just left class where they were just explaining that.

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3. What do the most abundant elements in Earth's atmosphere have in common?

Advocard [28]

Answer:

They all have: nitrogen :780,900 755,100

oxygen: 209,500 231,500

argon 9,300 12,800

carbon dioxide

386 591

8 0

3 years ago

Describe Rutherford's contribution to the atomic model.

Nady [450]

Answer:

Rutherford's experiment, also known as

$\alpha - scattering \: experiment$

supports the existence of neutrons and the nucleus.

Explanation:

In the above diagram, Rutherford was trying to explain his contributions using thin foils of gold and other metals as targets for alpha particles from a radioactive source.

He observed that the majority of particles penetrated the foil either undeflected or with only a slight deflection. But, every now and then an alpha particle was scattered(or deflected) at a large angle..

According to Rutherford, most of the atoms must be empty space. This explains why the majority of alpha particles passed through through the gold foil with little or no deflection. The atoms positive charges, Rutherford proposed are all concentrated in the Nucleus, which is a dense central core within the atom.

Whenever an alpha particle came close to a nucleus in the scattering experiment, it experienced a large repulsive force and therefore a large deflection. Moreover, an alpha particle coming towards a nucleus would be completely repelled and its direction would be reversed. The positively charged particles in the Nucleus are called Protons.

I hope you find this useful... Have a lovely day. 

4 0

3 years ago

Explain why we use 1/12 in finding atomic mass unit ?

Nat2105 [25]

Answer:

The u (amu is the old unit name) is 1/12 of the weight of an 12C atom. The way the u is chosen ensures that all core and atom masses are multiples of 1(±0.1) u.

Explanation:

Further explanation if needed...

Carbon 12 was chosen because the chemical atomic weights based on C12 are almost identical to the chemical atomic weights based on the natural mix of oxygen. Simply because the atomic mass is defined as 1/12 of the mass of 12C. Others isotopes of carbon (13C mostly, with an abundance of 1.1% approximately) account for an average atomic mass slightly above 12.

7 0

3 years ago

A first-order decomposition reaction has a rate constant of 0.00440 yr−1. How long does it take for [reactant] to reach 12.5% of

mina [271]

Answer:

473 year

Explanation:

Using integrated rate law for first order kinetics as:

$[A_t]=[A_0]e^{-kt}$

Where,

$[A_t]$ is the concentration at time t

$[A_0]$ is the initial concentration

Given:

To reach 12.5% of reactant means that 0.125 of $[A_0]$ is decomposed. So,

$\frac {[A_t]}{[A_0]}$ = 0.125

t = ?

$\frac {[A_t]}{[A_0]}=e^{-k\times t}$

$0.125=e^{-0.00440\times t}$

t = 473 year

8 0

3 years ago

How could you distinguish a compound from a mixture

ehidna [41]

Answer:

<h3>Compound are substances which can be formed by chemically combining two or more elements. Mixtures are substances that are formed by physically mixing two or more substances.</h3>

7 0

2 years ago

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