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Marrrta [24]
3 years ago
5

A 4.000 g sample of iron was heated from 0.0°C to 21.0°C. If it has a specific heat of 0.440 kJ/kg °C, how many kilojoules of he

at does it absorb?
Chemistry
1 answer:
Mashutka [201]3 years ago
6 0
M = 4 g = 4/1000 kg = 0.004 kg, θ₂ = 21.0°C, θ₁ = 0°C , c = 0.44kJ/kg°C,

Q = mc(θ₂ - θ₁)

Q = 0.004*0.440*(21 - 0)

Q  =  0.03696 kJ 

0.03696 kJ<span> of heat is absorbed.</span>
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2 years ago
How many moles of NaCl are present in 2.50 L of a 0.070 M solution?
posledela

Given :

Volume of NaCl solution 2.5 L .

Molarity of NaCl solution is 0.070 M .

To Find :

How many moles are present in the solution.

Solution :

Let, n be the number of moles.

We know, molarity is given by :

M = \dfrac{n}{V(in\ L)}

So,

n = M \times V\\\\n = 0.070\times 2.5 \\\\n = 0.175\ moles

Therefore, number of moles of NaCl is 0.175 moles.

6 0
3 years ago
How many liters of oxygen gas, at standard
Karo-lina-s [1.5K]

Answer:

Explanation:

  • For the balanced reaction:

<em>4Fe(s) + 3O₂(g) → 2Fe₂O₃(s)​.</em>

It is clear that 4 mol of Fe react with 3 mol of O₂ to produce 2 mol of Fe₂O₃.

  • Firstly, we need to calculate the no. of moles of 35.8 grams of Fe metal:

no. of moles of Fe = mass/molar mass = (35.8 g)/(55.845 g/mol) = 0.64 mol.

  • Now, we can find the no. of moles of O₂ is needed to react with the proposed amount of Fe:

<em><u>Using cross multiplication:</u></em>

4 mol of Fe is needed to react with → 3 mol of O₂, from stichiometry.

0.64 mol of Fe is needed to react with → ??? mol of O₂.

∴ The no. of moles of O₂ needed = (3 mol)(0.64 mol)/(4 mol) = 0.48 mol.

  • Finally, we can get the volume of oxygen using the information:

<em>It is known that 1 mole of any gas occupies 22.4 L at standard P and T (STP).</em>

<em></em>

<em><u>Using cross multiplication:</u></em>

1 mol of O₂ occupies → 22.4 L, at STP conditions.

0.48 mol of O₂ occupies → ??? L.

∴ The no. of liters of O₂ = (0.48 mol)(22.4 L)/(1 mol) = 10.752 L.

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3 years ago
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Answer:

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Explanation:

hope this is able to help you :)

6 0
2 years ago
Why do crystals form during crystallisation
Mazyrski [523]

Answer: Crystallization is a technique which chemists use to purify solid compounds. Crystals often form in nature when liquids cool and start to harden. Certain molecules in the liquid gather together as they attempt to become stable. They do this in a uniform and repeating pattern that forms the crystal. The process is based on the principles of solubility: compounds (solutes) tend to be more soluble in hot liquids (solvents) than they are in cold liquids. If a saturated hot solution is allowed to <u>cool</u>, the solute is no longer soluble in the solvent and forms crystals of pure compound. Impurities are excluded from the growing crystals and the pure solid crystals can be separated from the dissolved impurities by filtration.
For an example the salt we get from seawater can have many impurities in it. Hence, the process of crystallization is in use to remove these impurities.

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3 0
2 years ago
Read 2 more answers
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