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3 years ago

SCIENCEEEE!!!!! HELPPPP!!!!

Chemistry

2 answers:

Wittaler [7]3 years ago

7 0

Answer:

I would say Both are only physical changes.

Explanation:

Melting wax isn't creating a new substance, or changing the atomic structure. The wax is only changes from a solid to a liquid state. Sanding a piece if wood is usually done with sandpaper, which can physically be done with your hands. Hope this helped :)

IRINA_888 [86]3 years ago

5 0

pretty sure it's both are physical changes.

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50cm3 of 1 mol/dm3 HCl at 30°C was mixed with 50cm3 of 1mol/dm3 NaOH at 30°C in a styrofoam calorimeter. The temperature of the

trapecia [35]

Answer:

-21 kJ·mol⁻¹

Explanation:

Data:

H₃O⁺ + OH⁻ ⟶ 2H₂O

V/mL: 50 50

c/mol·dm⁻³: 1.0 1.0

ΔT = 4.5 °C

C = 4.184 J·°C⁻¹g⁻¹

C_cal = 50 J·°C⁻¹

Calculations:

(a) Moles of acid

$\text{Moles of acid} = \text{0.050 dm}^{3} \times \dfrac{\text{1.0 mol}}{\text{1 dm}^{3}} = \text{0.050 mol}\\\\\text{Moles of base} = \text{0.050 dm}^{3} \times \dfrac{\text{1.0 mol}}{\text{1 dm}^{3}} = \text{0.050 mol}$

So, we have 0.050 mol of reaction

(b) Volume of solution

V = 50 dm³ + 50 dm³ = 100 dm³

(c) Mass of solution

$\text{Mass of solution} = \text{100 dm}^{3} \times \dfrac{\text{1.00 g}}{\text{1 dm}^{3}} = \text{100 g}$

(d) Calorimetry

There are three energy flows in this reaction.

q₁ = heat from reaction

q₂ = heat to warm the water

q₃ = heat to warm the calorimeter

q₁ + q₂ + q₃ = 0

nΔH + mCΔT + C_calΔT = 0

0.050ΔH + 100×4.184×4.5 + 50×4.5 = 0

0.050ΔH + 1883 + 225 = 0

0.050ΔH + 2108 = 0

0.050ΔH = -2108

ΔH = -2108/0.0500

= -42 000 J/mol

= -42 kJ/mol

This is the heat of reaction for the formation of 2 mol of water

The heat of reaction for the formation of mol of water is -21 kJ·mol⁻¹.

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3 years ago

WHAT ARE SOME FUN ALCHSELTER EXPERIMENTS?

Vesna [10]

You can put an egg in Vinegar an egg in Olive oil

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3 years ago

Round 0.007062 to 4 significant numbers

mafiozo [28]

Answer

its already rounded

Explanation:

8 0

3 years ago

Which intermolecular force is characteristic of compounds which are liquids at room temperature and have relatively high boiling

SIZIF [17.4K]

Thew answer is hydrogen bonds.

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3 years ago

A 3.31-g sample of lead nitrate, Pb(NO3)2, molar mass = 331 g/mol, is heated in an evacuated cylinder with a volume of 2.53 L. T

Dahasolnce [82]

Answer:

0.486atm is the pressure of the cylinder

Explanation:

1 mole of Pb(NO₃)₂ descomposes in 4 moles of NO2 and 1 mole of O2. That is 1 mole descomposes in 5 moles of gas.

To find the pressure of the cylinder, we need to find moles of gas produced, and using general gas law we can determine the pressure of the gas:

Moles Pb(NO₃)₂ and moles of gas:

3.31g * (1mol / 331g) = 0.01 moles of Pb(NO₃)₂.

That means moles of gas produced is 0.05 moles.

Pressure of the gas:

Using PV = nRT

P = nRT/V

Where P is pressure (Incognite)

V is volume (2.53L)

R is gas constant (0.082atmL/molK)

T is absolute temperature (300K)

And n are moles of gas (0.05 moles)

P = 0.05mol*0.082atmL/molK*300K / 2.53L

P = 0.486atm is the pressure of the cylinder

3 0

3 years ago