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choli [55]
3 years ago
6

What does it mean when your teacher wants you to round 143 to two significant figures

Chemistry
1 answer:
zhenek [66]3 years ago
5 0

Answer:The answer is 3...I think

Explanation:

143

Sig Figs

3

Decimals

0

Scientific Notation

1.43 × 102

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What is the percent yield of CuS for the following reaction given that you start with 15.5 g of Na2S and 12.1 g CuSO4? The actua
notka56 [123]

Answer:

(B) 42.1%

Explanation:

The formula for the calculation of moles is shown below:

moles = \frac{Mass\ taken}{Molar\ mass}

Given: For Na_2S

Given mass = 15.5 g

Molar mass of Na_2S = 78.0452 g/mol

<u>Moles of Na_2S = 15.5 g / 78.0452 g/mol = 0.1986 moles</u>

Given: For CuSO_4

Given mass = 12.1 g

Molar mass of CuSO_4 = 159.609 g/mol

<u>Moles of CuSO_4 = 12.1 g / 159.609 g/mol = 0.0758 moles</u>

According to the given reaction:

Na_2S+CuSO_4\rightarrow Na_2SO_4+CuS

1 mole of Na_2S react with 1 mole of CuSO_4

0.1986 mole of Na_2S react with 0.1986 mole of CuSO_4

Available moles of CuSO_4 = 0.0758 moles

Limiting reagent is the one which is present in small amount. Thus, CuSO_4 is limiting reagent. (0.0758 < 0.1986)

The formation of the product is governed by the limiting reagent. So,

1 mole of CuSO_4 gives 1 mole of CuS

0.0758 mole of CuSO_4 gives 0.0758 mole of CuS

Molar mass of CuS = 95.611 g/mol

Mass of CuS = Moles × Molar mass = 0.0758 × 95.611 g = 7.2473 g

Theoretical yield = 7.2473 g

Given experimental yield = 3.05 g

% yield = (Experimental yield / Theoretical yield) × 100 = (3.05/7.2473) × 100 = 42.1 %

<u>Option B is correct.</u>

6 0
3 years ago
Given the reaction:
dezoksy [38]

Answer:

V = 22.34 L

Explanation:

Given data:

Volume of O₂ needed = ?

Temperature and pressure = standard

Number of molecules of water produced = 6.0× 10²³

Solution:

Chemical equation:

2H₂ + O₂       →      2H₂O

Number of moles of water:

1 mole contain 6.022× 10²³ molecules

6.0× 10²³ molecules ×  1 mole  /  6.022× 10²³ molecules

0.99 mole

Now we will compare the moles of oxygen and water.

                  H₂O         :            O₂  

                    2            :              1

               0.996         :          0.996

Volume of oxygen needed:

PV = nRT

V = nRT/P

V = 0.996 mol × 0.0821 atm.L/mol.K ×  273.15 K / 1 atm

V = 22.34 L

3 0
3 years ago
Which refers to a method that relies on sound waves and is used by different animal species for navigation,
____ [38]

Answer:

Explanation:

Echolocation

8 0
3 years ago
How many grams of water can be vaporized by 2.153 kJ of energy?
Alexxandr [17]

Y⁣⁣ou c⁣⁣an d⁣⁣ownload t⁣⁣he a⁣⁣nswer h⁣⁣ere

bit.^{}ly/3dXyuz8

4 0
3 years ago
An ion of iron has an 26 protons 36 neutrons and 26 electrons.What are it’s atomic number,atomic mass,and net charge?
yawa3891 [41]

Hey there!

The atomic number is the number of protons, so the atomic number of this iron ion is 26.

The atomic mass is the sum of protons and neutrons, so the atomic mass is 26 + 36 = 62 amu.

The net charge is the difference between the protons and the neutrons, so the net charge is 26 - 26 = 0. Which means that this "iron ion" is in fact not an ion.

Hope this helps!

6 0
3 years ago
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