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NikAS [45]
3 years ago
14

What is a physical change and how do you know it happened?

Chemistry
2 answers:
Ivan3 years ago
8 0
A physical change is when somebody smashes a computer screen. It's physical because the looks are changing of the computer. Hope this helps!
DedPeter [7]3 years ago
6 0
A physical change is defined as "a usually reversible change in the physical properties of a substance,as size or <span>shape" so its basically a change of a substance that you can see. You know a physical change has </span>occurred if a substance has changed size or shape or in a way that you can physically see.
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Identify the limiting reactant in the reaction of nitrogen and hydrogen to form NH3 if 5.23 g of N2 and 5.52 g of H2 are combine
Marrrta [24]

Answer:

1) The limiting reactant is N₂ because it is present with the lower no. of moles than H₂.

2) The amount (in grams) of excess reactant H₂ = 4.39 g.

Explanation:

  • Firstly, we should write the balanced equation of the reaction:

<em>N₂ + 3H₂ → 2NH₃.</em>

<em>1) To determine the limiting reactant of the reaction:</em>

  • From the stichiometry of the balanced equation, 1.0 mole of N₂ reacts with 3.0 moles of H₂ to produce 2.0 moles of NH₃.
  • This means that <em>N₂ reacts with H₂ with a ratio of (1:3).</em>
  • We need to calculate the no. of moles (n) of N₂ (5.23 g) and H₂ (5.52 g) using the relation:<em> n = mass / molar mass.</em>

The no. of moles of N₂ in (5.23 g) = mass / molar mass = (5.23 g) / (28.00 g/mol) = 0.1868 mol.

The no. of moles of H₂ (5.52 g) = mass / molar mass = (5.52 g) / (2.015 g/mol) = 2.74 mol.

  • From the stichiometry, N₂ reacts with H₂ with a ratio of (1:3).

The ratio of the reactants of N₂ (5.23 g, 0.1868 mol) to H₂ (5.52 g, 2.74 mol) is (1:14.67).

∴ The limiting reactant is N₂ because it is present with the lower no. of moles than H₂.

0.1868 mol of N₂ react completely with 0.5604 mol of H₂ and the remaining of H₂ is in excess.

<em>2) To determine the amount (in grams) of excess reactant of the reaction:</em>

  • As showed in the part 1, The limiting reactant is N₂ because it is present with the lower no. of moles than H₂.
  • Also, 0.1868 mol of N₂ react completely with 0.5604 mol of H₂ and the remaining of H₂ is in excess.
  • The no. of moles are in excess of H₂ = 2.74 mol - 0.5604 mol (reacted with N₂) = 2.1796 mol.
  • ∴ The amount (in grams) of excess reactant H₂ = n (excess moles) x molar mass = (2.1796 mol)((2.015 g/mol) = 4.39 g.

4 0
3 years ago
Plss help me asap!!!!​
Tanzania [10]

Answer:

Based on the evidence, the layers, of which the fossils were discovered, the climate was a beach before becoming a forest.

Explanation:

8 0
2 years ago
If 3.5 kJ of energy are added to a 28.2 g sample of iron at 20 degrees C, what is the final temperature of the iron in kelvins?
goldfiish [28.3K]

295.8k

that is the procedure above

3 0
3 years ago
Calculate the heat in joules "Q" needed to raise 27.0 g of water from 10.0 °C to 90.0 °C.​
Morgarella [4.7K]

Answer:

9028.8 J

Explanation:

The equation for working out the amount of thermal energy required is q = m c Δ T , where q is the amount of energy, m is the mass being heated up in grams, c is the specific heat capacity of what you're heating up in joules per gram per kelvin, and Δ T is the change in temperature in Kelvin.(Change in temperature will always give the same value,no matter Celsius or Kelvin)

mass = 27g, assuming specific heat capacity of water is 4.18 J/g*K, and the change in temperature is 90-10(=80)  , the energy needed to raise : 80 × 27 × 4.18 = 9028.8 J

5 0
3 years ago
What are the mass number of first 20 elements ?​
skelet666 [1.2K]

Answer:

The atomic mass (mₐ or m) is the mass of an atom. Although the SI unit of mass is the kilogram (symbol: kg), atomic mass is often expressed in the non-SI unit atomic mass unit (AMU) or unified mass (u) or dalton (symbol: Da), where 1 AMU or 1 u or 1 Da is defined as 1⁄12 of the mass of a single carbon-12 atom, at rest. The protons and neutrons of the nucleus account for nearly all of the total mass of atoms, with the electrons and nuclear binding energy making minor contributions.

7 0
2 years ago
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