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Mars2501 [29]
3 years ago
9

A 46.9 gram sample of a substance has a volume of about 3.5 centimeters3. It is solid at a room temperature of 23ºC. Out of the

four substances whose properties are given, which is the most likely identity of this substance? Substance Density (g/cm3) Melting Point (°C) Boiling Point (°C) molybdenum 10.28 2,623 4,639 mercury 13.53 -39 357 hafnium 13.31 2,233 4,603 lead 11.34 327 1,749 A. molybdenum B. mercury C. hafnium D. lead
Chemistry
2 answers:
Tpy6a [65]3 years ago
6 0

Answer:

It is (C) Hafnium

Explanation:

horrorfan [7]3 years ago
3 0

Answer : (C) Hafnium is the most likely identity of the given substance.

Solution :  Given,

Mass of given substance (m) = 46.9 g

Volume of given substance (V) = 3.5 Cm^{3}

First, find the Density of given substance.

Formula used :    

Density=\frac{\text{Mass of given substance}}{\text{Voume of given substance}}

Now,put all the values in this formula, we get

Density=\frac{46.9 g}{3.5 Cm^{3} } = 13.4 g/Cm^{3}

So, we conclude that the density of given substance (13.4 g/Cm^{3}) is approximately equal to the density of Mercury and Hafnium (13.53 and 13.31 g/Cm^{3} respectively).

According to the question the substance is solid at room temperature but Mercury is liquid at room temperature. So, Mercury is not identical to the given substance.

Another element i.e, Hafnium is the element whose density is approximately equal to the given substance and also solid at room temperature. And we know that the melting point of solid is high.

So, Hafnium is the most likely element which is the identity of the given substance.

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If you want to use a serial dilution to make a 1/50 dilution. The first dilution you make is a 1/5 dilution with a total volume
uranmaximum [27]

Answer:

0.2 mL stock solution, 0.8 solvent, 0.1 mL first solution and 0.9 solvent

Explanation:

The final volume for fist solution is 1 mL and concentration must will be 1/5, then 1 mL/5=0.2 mL. For complete the 1 mL add the missing solvent volume 1 mL-0.2 mL=0.8 mL. For second solution, assuming final volume is 1 mL, and concentration 1/10, then we have 1 mL /10=0.1 mL solution 1/5. Completing volume, 1 mL-0.1 mL= 0.9 mL solvent.

7 0
3 years ago
Consider the reaction given below.
Drupady [299]

Answer:

  • <u>K =  0.167 s⁻¹</u>

Explanation:

<u>1) Rate law, at a given temperature:</u>

  • Since all the data are obtained at the same temperature, the equilibrium constant is the same.

  • Since only reactants A and B participate in the reaction, you assume that the form of the rate law is:

        r = K [A]ᵃ [B]ᵇ

<u>2) Use the data from the table</u>

  • Since the first and second set of data have the same concentration of the reactant A, you can use them to find the exponent b:

        r₁ = (1.50)ᵃ (1.50)ᵇ = 2.50 × 10⁻¹ M/s

        r₂ = (1.50)ᵃ (2.50)ᵇ = 2.50 × 10⁻¹ M/s

         Divide r₂ by r₁:     [ 2.50 / 1.50] ᵇ = 1 ⇒ b = 0

  • Use the first and second set of data to find the exponent a:

        r₁ = (1.50)ᵃ (1.50)ᵇ = 2.50 × 10⁻¹ M/s

        r₃ = (3.00)ᵃ (1.50)ᵇ = 5.00 × 10⁻¹ M/s

        Divide r₃ by r₂: [3.00 / 1.50]ᵃ = [5.00 / 2.50]

                                  2ᵃ = 2 ⇒ a = 1

         

<u>3) Write the rate law</u>

  • r = K [A]¹ [B]⁰ = K[A]

This means, that the rate is independent of reactant B and is of first order respect reactant A.

<u>4) Use any set of data to find K</u>

With the first set of data

  • r = K (1.50 M) = 2.50 × 10⁻¹ M/s ⇒ K = 0.250 M/s / 1.50 M = 0.167 s⁻¹

Result: the rate constant is K =  0.167 s⁻¹

6 0
3 years ago
Use your calculator to determine the answer to the following calculation:<br> 1.0×10^−15/4.2×10^−7
lianna [129]
1.0×10^−15/4.2×10^−7=<span>2.3809524e-23 Hoped I helped!</span>
8 0
3 years ago
Help me please guys :)
nika2105 [10]

Explanation:

1. Methane

2. Diamond

3. not sure : )

6 0
3 years ago
Which of the following processes is exothermic?
Elodia [21]

Answer:

a. The reaction associated with DHºf for an ionic compound

Explanation:

An exothermic process is a process that loses heat for the surroundings, so the temperature of the system must decrease, and ΔH must be negative.

DHºf or ΔHºf of an ionic compound is always negative because the final energy is always lower than the initial. It happens because of the stability of the bond, the system wants a lower energy state to be stable.

The ionization of a lithium atom occurs with the gain of energy, which is given to the electron, so it may give off the atom. So it's an endothermic process.

To change the state of a solid to a gas (sublimation), the compound must gain heat, its temperature must increase, so it's always an endothermic process.

To break a covalent bond it's necessary the gain of energy, so it's an endothermic process.

8 0
3 years ago
Read 2 more answers
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