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V125BC [204]
2 years ago
6

Please help, I'm confused and it's due very soon!

Chemistry
1 answer:
ryzh [129]2 years ago
3 0

Answer:

1. Lanthanum-139 atom is the stable isotope of lanthanum with relative atomic mass 138.906348, 99.9 atom percent natural abundance and nuclear spin 7/2.

2. In fact, over 80% of electric cars sold globally utilized permanent magnet-based motors in 2019. These magnets are typically made with rare-earth materials such as neodymium and dysprosium, which have a very geographically constrained supply chain.

3. It is the second most reactive of the rare-earth metals after europium. Lanthanum oxidizes in air at room temperature to form La2O3. It slowly reacts with water and quickly dissolves in diluted acids, except hydrofluoric acid (HF) because of formation of a protective fluoride (LaF3) layer on the surface of the metal.

Explanation:

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Weight in grams of NaCl
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Answer: 58.44g

Explanation: The molar mass of NaCl is 58.44g.

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3 years ago
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PLS HELP-CHEMISTRY: What is the molar concentration of an ammonia solution in which there are 0.1557 grams
harina [27]

Answer: M = 0.036 M

Explanation: Solution attached:

First convert mass of NH3 to moles

Next convert volume in mL to L

Use the formula for Molarity

M = n / L

4 0
3 years ago
NH4NO3, whose heat of solution is 25.7 kJ/mol, is one substance that can be used in cold pack. If the goal is to decrease the te
makvit [3.9K]

Answer:

There are necessaries 35,2g of NH₄NO₃ per 100,0g of water to decrease the temperature of the solution from 25,0°C to 5,0°C

Explanation:

To decrease the temperature of the solution there are necessaries:

4,184J/g°C×(5,0°C-25,0°C)×(100,0g+X) = -Y

8368J + 83,68J/gX = Y <em>(1)</em>

Where x are grams of NH₄NO₃ you need to add and Y is the energy that you need to decrease the heat.

Also, the energy Y will be:

Y = 25700J/mol×\frac{1mol}{80,043g}X

Y = 321J/g X <em>(2)</em>

Replacing (2) in (1)

8368J + 83,68J/g X = 321J/g X

8363J = 237,32J/gX

<em>X = 35,2g</em>

<em />

Thus, there are necessaries 35,2g of NH₄NO₃ per 100,0g of water to decrease the temperature of the solution from 25,0°C to 5,0°C

I hope it helps!

6 0
3 years ago
What geological process(es) could form magnesium silicate perovskite at 500 C?
dimulka [17.4K]

Magnesium silicate is a compound of magnesium oxide and silicon. It is the magnesium salt of silicic acid containing an unspecified amount of water. The molecular formula can be expressed more clearly as MgSiO3.

7 0
2 years ago
What is the activation energy of this reaction? 10 kJ 25 kJ 30 kJ 35 kJ
Nostrana [21]

Answer:

25 kj

Explanation:

8 0
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