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3 years ago

The name of the commonly used hardness scale is:

Chemistry

2 answers:

Wittaler [7]3 years ago

7 0

The name of the commonly used hardness scale is: Mohs, or Mohs hardness scale

hope this helps

Elza [17]3 years ago

7 0

Answer: Option (c) is the correct answer.

Explanation:

Mohs scale is used to determine the hardness of a material or substance.

This scale includes ten materials and each of them are placed according to their hardness from bottom to top as follows.

Talc = 1
Gypsum = 2
Calcite = 3
Fluorite = 4
Apatite = 5
Orthoclase = 6
Quartz = 7
Topaz = 8
Corundum = 9
Diamond = 10

Greater is the number, the hardest will be the substance, that is, according to Mohs scale diamond is the hardest substance and talc is the least hardest substance.

Thus, we can conclude that option (c) is the correct answer.

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Read the given equation. 2Na + 2H2O ? 2NaOH + H2 During a laboratory experiment, a certain quantity of sodium metal reacted with

emmasim [6.3K]

Answer:

The number of moles of Na metal that used initially = 0.70 mol.

The quantity of Na metal used initially to produce 7.80 of H₂ gas = 16.02 g.

Explanation:

It is a stichiometry problem.

2Na + 2H₂O → 2NaOH + H₂,

The balanced equation shows that 2.0 moles of Na metal react with 2.0 moles of water to produce 2.0 moles of NaOH and 1.0 mole of H₂,

Firstly, we need to convert the volume of H₂ (7.80 L) produced to no. of moles (n) using the ideal gas law: PV = nRT,

where, P is the pressure of the gas in atm (P at STP = 1.0 atm),

V is the volume of the gas in L (V = 7.80 L),

n is the number of moles in mole,

R is the general gas constant (R = 0.082 L.atm/mol),

T is the temperature of the gas in K (T at STP = 0.0 °C + 273 = 273.0 K).

∴ The number of moles of H₂ gas (n) = PV / RT = [(1.0 atm)(7.80 L)] / [(0.082 L.atm/mol.K)(273.0 K)] = 0.35 mol.

Using cross multiplication:

2.0 moles of Na will produce → 1.0 mole of H₂, from the stichiometrey.

??? moles of Na will produce → 0.35 mole of H₂.

∴ The number of moles of Na metal that used initially = (2.0 mol)(0.35 mol) / (1.0 mol) = 0.70 mol.

Now, we can get the quantity of Na metal using the relation:

∴ mass = n x molar mass = (0.70 mol)(22.989 g/mol) = 16.02 g.

6 0

3 years ago

The half-life of a certain tranquilizer in the bloodstream is 5050 hours. how long will it take for the drug to decay to 8686%

Novosadov [1.4K]

Using the exponential decay model; we calculate "k"
We know that "A" is half of A0
A = A0 e^(k× 5050)
A/A0 = e^(5050k)
0.5 = e^(5055k)
In (0.5) = 5055k
-0.69315 = 5055k
k = -0.0001371
To calculate how long it will take to decay to 86% of the original mass
0.86 = e^(-0.0001371t)
In (0.86) = -0.0001371t
-0.150823 = -0.0001371 t
t = 1100 hours

4 0

2 years ago

If the frequency of a wave is 68 hertz then the period of the wave is going to be

tigry1 [53]

The answer is 4.41x10^1 m.

Explanation:

You would use this formula to calculate it
λ = C/f

Where,

λ (Lambda) = Wavelength in meters

c = Speed of Light (299,792,458 m/s)

f = Frequency

So we have the frequency, 68 Hz, and we have the speed of light. Now we put it into the equation and it will look like this:

λ= (299,792,458 m/s) / (68 Hz)

λ= 4.41x10^1

6 0

3 years ago

Read 2 more answers

g aqueous barium hydroxide (ba(oh)2) and nitric acid (hno3) participate in a complete neutralization reaction. in the molecular

Whitepunk [10]

Answer:

Where the products are H2O and Ba(NO3)2

Explanation:

A base, as, barium hydroxide (Ba(OH)2) reacts with an acid (HNO3), producing water (H2O), and the related salt (Ba(NO3)2) in a reaction called neutralization reaction.

The balanced reaction is:

Ba(OH)2 + 2 HNO3 → 2 H2O + Ba(NO3)2

Where the products are H2O and Ba(NO3)2

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3 years ago

Why does the sun seem to change position in the sky?

Blababa [14]

The first major contributor to the Sun's apparent motion is the fact that Earth orbits the Sun while tilted on its axis. The Earth's axial tilt of approximately 23.5° ensures that observers at different locations will see the Sun reach higher-or-lower positions above the horizon throughout the year.

hope this helps ^^

7 0

2 years ago

Read 2 more answers