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hodyreva [135]
3 years ago
6

The total number of each element is not changed during a chemical reaction

Chemistry
1 answer:
Paha777 [63]3 years ago
3 0

false all element when they are combined eachother thier valance number will change

the combination of oxygen and aluminum gives us Al2O3 see even the numbers are changing thank you if you have a comment you can write

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__ Cu + ___ HNO₃ → ___ _Cu(NO₃)₂ + ___ NO₂ + ___ H₂O
ivolga24 [154]

Answer:

Cu + 4HNO3 --->   Cu(NO3)2 + 2NO2 + 2H2O.

Explanation:

Balancing:

Cu + 4HNO3 --->   Cu(NO3)2 + 2 NO2 + 2H2O.

3 0
3 years ago
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A certain radioactive element has a half-life of one hour. If you start with 40.0 grams of the element at noon, how much of the
Tpy6a [65]

If you start with 40.0 grams of the element at noon, 10.0 grams radioactive element will be left at 2 p.m. The correct answer between all the choices given is the second choice or letter B. I am hoping that this answer has satisfied your query and it will be able to help you in your endeavor, and if you would like, feel free to ask another question.

5 0
3 years ago
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how many milliliters of 1.50 m hno3 contain enough nitric acid to dissolve an old copper penny with a mass of 3.94 g?
Lerok [7]
Molar mass HNO₃ = 63.0 g/mol

number of moles = 3.94 / 63.0 => 0.0625 moles

Volume = moles / molarity

V = 0.0625 / 1.50

V = 0.04166 L x 1000 = 41.66 mL

hope this helps!

5 0
3 years ago
When nahco3 completely decomposes, it can follow this balanced chemical equation: 2nahco3 → na2co3 h2co3 determine the theoretic
BigorU [14]

Theoretical yield = 2.397

The product could be sodium carbonate

percent yield = 98.456%

When nahco3 completely decomposes, it can follow this balanced chemical equation:

2nahco3 → na2co3 h2co3

If the mass of the NaHCO3 sample is 3.80 g, we must use stoichiometry to calculate the theoretical yields of each of the products.

mass of NaHCO₃ = 3.80 g

molar mass of NaHCO₃ = 84 g/mol

so the no of moles of NaHCO₃ = 3.80/84 =  0.0452 mol

You see, one mole of sodium carbonate and one mole of hydrogen carbonate are produced from two moles of sodium bicarbonate.

so, the no of moles of sodium carbonate = 0.0452/2 = 0.0226 mol

∴ mass of sodium carbonate ( Na₂CO₃) = no of moles of Na₂CO₃ × molar mass of Na₂CO₃

=  0.0226 × 106 ≈ 2.397 g

no of moles of hydrogen carbonate = 0.0452/2 = 0.0226 mol

mass of the hydrogen carbonate ( H₂CO₃) = no of moles of H₂CO₃ × molar mass of H₂CO₃

= 0.0226 × 62 g = 1.401 g

mass of one of the products was measured to be 2.36 g , from above data, we can say it must be sodium carbonate because value is the nearest of 2.397 g.

percentage yield = experimental yield/theoretical yield × 100

here experimental yield of Na₂CO₃ = 2.36 g

and theoretical yield of Na₂CO₃ = 2.397 g

∴ % yield = 2.36/2.397 × 100 ≈ 98.456%

Therefore the percentage yield of the product is 98.456%

To learn more about percentage yield visit:

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6 0
2 years ago
What functions of cells can be affected by a mutation?
Colt1911 [192]
It changes the rate of growth that cells usually undergo.
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3 years ago
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