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Luden [163]
3 years ago
7

Why can't chemical changes be reversed?

Chemistry
1 answer:
Temka [501]3 years ago
7 0
<span>a chemical change results in the formation of one or more new substances</span>
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How many grams of h2 will be produced if 175g of HCI are allowed to react completely with sodium
Sedbober [7]

Answer:

4.8 grams of H₂ will be produced if 175g of HCI are allowed to react completely with sodium

Explanation:

By stoichiometry of the reaction (that is, the relationship between the amount of reagents and products in a chemical reaction) you can see that the following amounts in moles of each compound react and are produced:

  • HCl: 2 moles
  • Na: 1 mole
  • NaCl: 2 moles
  • H₂: 1 mole

You know the following masses of each element:

  • H: 1 g/mole
  • Cl: 35.45 g/mole
  • Na: 23 g/mole

So, the molar mass of each compound participating in the reaction is:

  • HCl: 1 g/mole + 35.45 g/mole= 36.45 g/mole
  • Na: 23 g/mole
  • NaCl: 23 g/mole + 35.45 g/mole= 58.45 g/mole
  • H₂: 2* 1 g/mole= 2 g/mole

Then, by stoichiometry of the reaction, the following amounts in grams of each of the compounds participating in the reaction react and are produced:

  • HCl: 2 moles* 36.45 g/mole= 72.9 g
  • Na: 1 mole* 23 g/mole= 23 g
  • NaCl: 2 moles* 58.45 g/mole= 116.9 g
  • H₂: 1 mole* 2 g/mole= 2 g

So, a rule of three applies as follows: if by stoichiometry, when reacting 72.9 grams of HCl 2 grams of H₂ are formed, when reacting 175 grams of HCl how much mass of H₂ will be formed?

mass of H_{2} =\frac{175 g of HCl*2g ofH_{2} }{72.9 g of HCl}

mass of H₂= 4.8 g

<u><em>4.8 grams of H₂ will be produced if 175g of HCI are allowed to react completely with sodium</em></u>

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2 years ago
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Sergeeva-Olga [200]
I believe the answer is A (it was on another Brainly question as well).
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3 years ago
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Liono4ka [1.6K]
It actually depends on the percentage of the concentration give. Percentages can be expressed as %mass/mass, %volume/volume or %mass/volume. To keep things simple, let's just assume that it is in %volume/volume. Thus, 13% of 520 mL is pure acid.

Volume of pure acid = 520*0.13 = 67.6 mL
4 0
2 years ago
How many grams (m) of glucose are in 165 ml of a 5.50% (m/v) glucose solution? express your answer numerically in grams?
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     <span> mass of glucose = 0.055 *165 = 9.075 g

vol of methyl alc = 0.185 * 1.87 = 0.346 L = 346 ml

% NaCl ( m/v ) = mass NaCl * 100/ vol of soln

or Vol of Soln = mass NaCl / % NaCl (m/v)

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Answer:

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