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zzz [600]
3 years ago
7

A material has a volume of 63.0 cm3 and a mass of 28 grams.  What is the density of the material in g/cm3 to the correct number

of significant figures?
Chemistry
1 answer:
dimaraw [331]3 years ago
7 0

Answer:

0.4444 g/cm³ ≅ 0.44 g/cm³ (2 significant figures).

Explanation:

  • Knowing that:

<em>d = m/V,</em>

where, d is the density of the material (g/cm³).

m is the mass of the material (m = 28 g).

V is the volume of the material (V = 63.0 cm³).

<em>∴ d = m/V </em>= (28 g)/(63.0 cm³) = <em>0.4444 g/cm³ ≅ 0.44 g/cm³ (2 significant figures).</em>

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What is the composition, in atom percent, of an alloy that consists of a) 5.5 wt% Pb and b) 94.5 wt% of Sn? Assume that the atom
Anastaziya [24]

Answer : The percent composition of Pb and Sn in atom is, 3.21 % and 96.8 % respectively.

Explanation :

First we have to calculate the number of atoms in 5.5 wt% Pb and 94.5 wt% of Sn.

As, 207.2 g of lead contains 6.022\times 10^{23} atoms

So, 5.5 g of lead contains \frac{5.5}{207.2}\times 6.022\times 10^{23}=1.59\times 10^{22} atoms

and,

As, 118.71 g of lead contains 6.022\times 10^{23} atoms

So, 94.5 g of lead contains \frac{94.5}{118.71}\times 6.022\times 10^{23}=4.79\times 10^{23} atoms

Now we have to calculate the percent composition of Pb and Sn in atom.

\% \text{Composition of Pb}=\frac{\text{Atoms of Pb}}{\text{Atoms of Pb}+\text{Atoms of Sn}}\times 100

\% \text{Composition of Pb}=\frac{1.59\times 10^{22}}{(1.59\times 10^{22})+(4.79\times 10^{23})}\times 100=3.21\%

and,

\% \text{Composition of Sn}=\frac{\text{Atoms of Sn}}{\text{Atoms of Pb}+\text{Atoms of Sn}}\times 100

\% \text{Composition of Sn}=\frac{4.79\times 10^{23}}{(1.59\times 10^{22})+(4.79\times 10^{23})}\times 100=96.8\%

Thus, the percent composition of Pb and Sn in atom is, 3.21 % and 96.8 % respectively.

6 0
3 years ago
Car manufacturers are developing engines that use H₂ as fuel. In Iceland, Sweden, and other parts of Scandinavia, where hydroele
weeeeeb [17]

If the coulombs are supplied at 1.44 V, then 4.766 × 10¹¹ joules are produced.

(a) The reaction is

2H₂O + 2e⁻ → H₂ + 2OH⁻

According to the reaction, 2 moles of electrons flow per mole of reaction,

(b) Given

T = 25°C

Change Celsius into Kelvin

T = 25°C

   = (25 + 273 ) K

   = 298 K

<h3>What is Ideal Gas Law ?</h3>

It is expressed as

PV = nRT

Hence ,

n = \frac{PV}{RT}

   = \frac{(12)(3.5.10^{6} )}{(0.082057)(298)}

   = 1.7176 ×10⁶ mole

Now, From the given reaction we can say that ,1 mole of H₂  is produced by 2 moles of electron

Hence, 1.7176 × 10⁶ mole of H₂ is produced by

= 2 × 1.7176 × 10⁶ moles of  electron

= 3.435 ×10⁶ moles of electron

We know that

charge = moles of electron × F

          =  (3.435 ×10⁶ × 96500) C

           =  3.31 × 10¹¹ C

(c) We know that,

Voltage = \frac{energy}{charge}  =  \frac{J}{C}

1.44 V = \frac{energy}{3.31 . 10^{11} }

Energy = 1.44 V × 3.31 × 10¹¹ C

            =  4.766 × 10¹¹ Joules

Thus from the above conclusion we can say that, coulombs are supplied at 1.44 V, then 4.766 × 10¹¹ joules are produced.

Learn more about Fuel Cell here : brainly.com/question/16612142

#SPJ4

Disclaimer : The question given was incomplete on portal, Here is the complete question.

Question : Car manufacturers are developing engines that use H₂ as fuel. In Iceland, Sweden, and other parts of Scandinavia countries, where hydroelectric plants produce inexpensive electric power, the H₂ can be made industrially by the electrolysis of water.

a) How many moles of electrons flow per mole of reaction ?

b) How many coulombs are needed to produce 3.53X10⁶ L of H₂ gas at   12.0 atm and 25°C.

c) If the coulombs are supplied at 1.44 V, how many joules are produced?

8 0
2 years ago
When active metals such as magnesium are immersed in acid solution, hydrogen gas is evolved. Calculate the volume of H2(g) at 30
V125BC [204]

Answer:

The volume of  H₂ (g) obtained is 22.4L

Explanation:

First of all, think the reaction:

2HCl (aq) + Zn (s) → ZnCl₂ (aq)  + H₂ (g)

You have to add a 2, in the HCl to get ballanced.

Now we should know how many moles of each reactant, do we have.

Volume . Molarity = moles

Notice that volume is in mL, so I must convert to L.

275 mL = 0.275L

0.275L . 0.725mol/L = 0.2 moles of HCl

Molar mass of Zn: 65.41 g/m

50 g / 65.41 g/m = 0.764 moles

Ratio between reactants is 2:1, so I need the double of moles of HCl to react, and a half moles of Zn to react.

My limiting reactant is the HCl, for 0.764 moles of Zinc, I need 1.528 (0.764 .2) of HCl, and I only have 0.2 moles.

Ratio between HCl and H₂ is 1:1, so 0.2 HCl make 0.2 moles of gas

Now apply the Ideal Gas Law, to find out the volume

P. V = n . R . T

2 atm . V = 0.2 mol . 0.08206L atm/K mol . 273K

V =  (0.2 mol . 0.08206L atm/K mol . 273K ) / 2 atm

V = 2.24 L

4 0
3 years ago
How many moles of PC15 can be produced from 58.0 g of Cl₂ (and excess<br> P4)?
ludmilkaskok [199]

0.3268 moles of PC15 can be produced from 58.0 g of Cl₂ (and excess

P4)

<h3>How to calculate moles?</h3>

The balanced chemical equation is

P_{4}  + 10Cl_{2}  = 4PCl_{5}

The mass of clorine is m(Cl_{2}) = 58.0 g

The amount of clorine is n(Cl_{2}) = m(Cl_{2})/M(Cl_{2}) = 58/70.906 = 0.817 mol

The stoichiometric reaction,shows that

10 moles of Cl_{2} yield 4 moles of PCl_{5};

0.817 of Cl_{2} yield x moles of PCl_{5}

n(PCl_{5}) = 4*0.817/10 = 0.3268 mol

To know more about stoichiometric reaction, refer:

brainly.com/question/14935523

#SPJ9

3 0
1 year ago
Please help it’s due today I will give brainliest
Thepotemich [5.8K]

1st and 4th options are suitable answers, as these 2 changes are not exactly physical changes as it cant return back to original form and as well as its not cooling, so I feel its 1st and 4th options

7 0
3 years ago
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