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Rina8888 [55]
2 years ago
14

What do astronomers use to calculate the age of the universe? Check all that apply. dark energy the age of rocks on Earth the ag

e of the oldest stars patterns of background radiation how fast distant galaxies are moving away from us
Chemistry
2 answers:
Hitman42 [59]2 years ago
4 0

The answers are:

The age of the oldest stars

How fast distant galaxies are moving away from us

Patterns of background radiation

Using these techniques, and using the Big Bang as reference point, astronomers estimate that the universe may be approximately 12 billion years old.


Likurg_2 [28]2 years ago
4 0

the age of the oldest stars

patterns of background radiation

how fast distant galaxies are moving away from us

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Explain the difference between fixed and variable oxidation
dem82 [27]

Fixed vs Variable Oxidation is given below.

Explanation:

1.In its compounds, hydrogen has an oxidation number of +1, except. hydrides where the. oxidation number of hydrogen is -1. In their compounds, the metals with fixed oxidation states have the oxidation number that. corresponds with the fixed oxidation number.

A variable oxidation state is a value that determines the charge of the atom depending on certain conditions.

2. Ox­i­da­tion state of el­e­ments is con­sid­ered to be of the most im­por­tant in the study of chem­istry. For some el­e­ments, this fig­ure is con­stant known as fixed oxidation , while for oth­ers it is vari­able is called variable oxidation state.

3. MgCl2 :  magnesium is in Group IIA and all elements in Group IIA have fixed oxidation numbers of +2

FeCl2 :  iron has a variable oxidation number of either +2 or +3 and is not fixed

7 0
3 years ago
Sodium hydride reacts with excess water to produce aqueous sodium hydroxide and hydrogen gas:NaH (s) H2O (l) → NaOH (aq) H2 (g)A
Anuta_ua [19.1K]

NaH(s)+ H2O (l)=>NaOH(aq)+H2(g)

You want to calculate the mass of NaH, I assume.  Otherwise, the question isn't clear.  It simply says calculate the mass(??)

 

So, calculate the moles of H2 gas that satisfy the conditions of 982 ml at 28ºC and 765 torr.  But you must subtract the vapor pressure of water at 28º to get the actual pressure of the H2 gas.  So, the actual conditions are 982 ml (0.982 L) and 301 K and 765-28 = 737 torr.

PV = nRT

n = PV/RT = (737 torr)(0.982 L)/(62.4 L-torr/Kmol)(301 K)

n = 0.0385 moles H2

 

moles NaH needed = 0.0385 moles H2 x 1 mole NaH/mole H2 = 0.0385 moles NaH required

mass of NaH needed = 0.0385 moles x 24 g/mole = 0.925 g NaH

Brainliest Please :)

7 0
3 years ago
Read 2 more answers
Balance the following chemical reaction:
mrs_skeptik [129]

Answer:

what the freak is thisnenejehey

7 0
3 years ago
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In Niels Bhor's model of the atom, electrons move
exis [7]
Bohrs model says that electrons move in fixed shells (which have fixed distances) around the nucleus of an atom. 
5 0
3 years ago
Contrast (Compare) the Sun's gravitational pull on Earth when Earth is
77julia77 [94]

Answer:

gravity equation.

Explanation:

use this gravity equation

F= G(m1*m2/d²)

3 0
2 years ago
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