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belka [17]
3 years ago
15

Which of the following are indicators of a chemical change?

Chemistry
1 answer:
Ket [755]3 years ago
4 0

Answer:

All unexpected changes: color change (two clear liquids make purple), temperature change, Odor change or formation, precipitate formation (solid forms), and the production of gas.

Explanation:

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How many particles would be found in a 89.2 g sample of Na?
julsineya [31]
One mole of a substance contains 6.02 × 10∧23 particles. Thus we first convert  89.2 g to moles. 1 mole of sodium contains 23 g
Hence 89.2 g = 89.2 / 23 g = 3.878 moles
Therefore, 3.878 × 6.02×10∧23 particles= 23.346 × 10∧23 particles
Hence 89.2 g of sodium contains 2.335 ×10∧24 particles 
5 0
3 years ago
A volume of 125 mL of H2O is initially at room temperature (22.00 ∘C). A chilled steel rod at 2.00 ∘C is placed in the water. If
VMariaS [17]

Answer:

41.9 g

Explanation:

We can calculate the heat released by the water and the heat absorbed by the steel rod using the following expression.

Q = c × m × ΔT

where,

c: specific heat capacity

m: mass

ΔT: change in temperature

If we consider the density of water is 1.00 g/mol, the mass of water is 125 g.

According to the law of conservation of energy, the sum of the heat released by the water (Qw) and the heat absorbed by the steel (Qs) is zero.

Qw + Qs = 0

Qw = -Qs

cw × mw × ΔTw = -cs × ms × ΔTs

(4.18 J/g.°C) × 125 g × (21.30°C-22.00°C) = -(0.452J/g.°C) × ms × (21.30°C-2.00°C)

ms = 41.9 g

3 0
3 years ago
HELP!! SYNTHESIS QUIZ!!
Juliette [100K]
Ok it’s 38 so I hope that helps ok
6 0
3 years ago
In the presence of excess oxygen, methane gas burns in a constant-pressure system to yield carbon dioxide and water: CH4 (g) 2O2
Degger [83]

Answer:

The energy released will be -94.56 kJ or -94.6 kJ.

Explanation:

The molar mass of methane is 16g/mol

The given reaction is:

CH_{4}(g) + 2O_{2} (g) --> CO_{2} (g)+ 2H_{2}O(l)

the enthalpy of reaction is given as  ΔH = -890.0 kJ

This means that when one mole of methane undergoes combustion it gives this much of energy.

Now as given that the amount of methane combusted = 1.70g

The energy released will be:

=\frac{energy released by one moleXgiven mass}{molarmass} =\frac{-890X1.7}{16}= -94.56 kJ

7 0
3 years ago
Which of the following should have the highest conductivity? a. 3.0 M NaCl b. 2.1 M Na3PO4 c. 2.4 M CaCl2 d. 3.2 M NH4NO3
Aleks [24]

Answer:

The correct answer is option b, that is, 2.1 M Na₃PO₄.

Explanation:

The solution with the largest concentration of ions will possess the highest conductivity.

a) 3.0 M NaCl

NaCl ⇔ Na⁺ + Cl⁻

Here the total number of ions is 2, therefore, the concentration of ions is 3.0 × 2 = 6.0 M

b) 2.1 M Na₃PO₄

Na₃PO₄ ⇔ 3 Na⁺ + PO₄³⁻

Here the total number of ions i 4. Therefore, the concentration of ions is

2.1 × 4 = 8.4 M.

c) 2.4 M CaCl₂

CaCl₂ ⇔ Ca²⁺ + 2Cl⁻

The total number of ions is 3. Therefore, the concentration of ions is

2.4 × 3 = 7.2 M

d) 3.2 M NH₄NO₃

NH₄NO₃ ⇔ NH₄⁺ + NO₃⁻

The total number of ions is 2. The concentration of ions will be,

3.2 × 2 = 6.4 M

Hence, the highest conductivity will be of 2.1 M Na₃PO₄.

8 0
3 years ago
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