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3 years ago

How do scientists use the Doppler affect to understand the universe?

1 answer:

8 0

Astronomers use the Doppler effect to measure the frequency of light waves as an object is moving with respect to the observer

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I need help on balacing equations

nevsk [136]

Answer: sorry hun can’t help with this I was asked different questions when I learned this :,)

Explanation: have a nice day

8 0

2 years ago

2. What group is the atom in? 2 or 2A 6 14 1

Juliette [100K]

Answer:

$\Large \boxed{\mathrm{Group \ 4}}$

Explanation:

The number of valence electrons tells us the group number of the neutral atom.

The atom has 4 valence electrons.

The atom is in group 4.

5 0

3 years ago

Read 2 more answers

What kind of questions CANNOT be answered by chemistry?

Sergeu [11.5K]

Answer:

d. why matter exists

Explanation:

The kind of questions that chemistry CANNOT answer is "why matter exists".

In Chemistry, question of how the properties, composition and structure of substances are is answered. Also, the transformations that these substances undergo, and the energy that they release or absorbe during the transformation processes are revealed in chemistry.

Chemistry can answer the question of what forms of matter exists but cannot answer why matter actually exists.

5 0

3 years ago

Define equilibrium. plz and thxxx

Serggg [28]

Answer:

Equilibrium is the state of balance. Where opposing forces cancel each other out and no changes are occurring.

Good luck, hope this helps :)

5 0

2 years ago

Read 2 more answers

Calculate the enthalpy of the reaction

harkovskaia [24]

Answer : The enthalpy of the reaction is, -2552 kJ/mole

Explanation :

According to Hess’s law of constant heat summation, the heat absorbed or evolved in a given chemical equation is the same whether the process occurs in one step or several steps.

According to this law, the chemical equation can be treated as ordinary algebraic expression and can be added or subtracted to yield the required equation. That means the enthalpy change of the overall reaction is the sum of the enthalpy changes of the intermediate reactions.

The given enthalpy of reaction is,

$4B(s)+3O_2(g)\rightarrow 2B_2O_3(s)$ $\Delta H=?$

The intermediate balanced chemical reactions are:

(1) $B_2O_3(s)+3H_2O(g)\rightarrow 3O_2(g)+B_2H_6(g)$ $\Delta H_A=+2035kJ$

(2) $2B(s)+3H_2(g)\rightarrow B_2H_6(g)$ $\Delta H_B=+36kJ$

(3) $H_2(g)+\frac{1}{2}O_2(g)\rightarrow H_2O(l)$ $\Delta H_C=-285kJ$

(4) $H_2O(l)\rightarrow H_2O(g)$ $\Delta H_D=+44kJ$

Now we have to revere the reactions 1 and multiple by 2, revere the reactions 3, 4 and multiple by 2 and multiply the reaction 2 by 2 and then adding all the equations, we get :

(when we are reversing the reaction then the sign of the enthalpy change will be change.)

The expression for enthalpy of the reaction will be,

$\Delta H=-2\times \Delta H_A+2\times \Delta H_B-6\times \Delta H_C-6\times \Delta H_D$

$\Delta H=-2(+2035kJ)+2(+36kJ)-6(-285kJ)-6(+44)$

$\Delta H=-2552kJ$

Therefore, the enthalpy of the reaction is, -2552 kJ/mole

4 0

3 years ago