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avanturin [10]
3 years ago
15

Substances that can carry electric current under some conditions but not under others are called semiconductors.

Chemistry
1 answer:
Dmitry [639]3 years ago
8 0
A semiconductor is a substance, usually a solid chemical element or compound, that can conduct electricity under some conditions but not others, making it a good medium for the control of electrical current. Silicon is a very common element -- for example, it is the main element in sand and quartz.
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A 4.48 L sample of HCl gas, measured at STP, is dissolved in enough water to produce 400.0 mL of solution. A 25.0 mL sample of t
serious [3.7K]

Answer:

27.53 mL.

Explanation:

  • Firstly, we need to calculate the no. of moles of HCl using the general law of ideal gas: <em>PV = nRT.</em>

where, P is the pressure of the gas in atm (P = 1.0 atm at STP).

V is the volume of the gas in L (4.48 L).

n is the no. of moles of the gas in mol.

R is the general gas constant (R = 0.0821 L.atm/mol.K),

T is the temperature of the gas in K (T = 273 K at STP).

<em>∴ n = PV/RT </em>= (1.0 atm)(4.48 L)/(0.0821 L.atm/mol.K)(273 K) = <em>0.1998 mol ≅ 0.12 mol.</em>

<em>∴ The concentration of 0.12 mol HCl in 400.0 mL water = n/V = </em>(0.12 mol)/(0.4 L) <em>= 0.499 ≅ 0.50 mol/L.</em>

  • At equivalence: the no. of millimoles of HCl = the no. of millimoles of Sr(OH)₂.

<em>(MV)HCl = (xMV) Sr(OH)₂</em>

∴ The volume of Sr(OH)₂ = (MV)HCl/(xM) Sr(OH)₂ = (25.0 mL)(0.50 mol/L)/(2)(0.227 M) = 27.53 mL.

8 0
4 years ago
The table shows the amount of radioactive element remaining in a sample over a period of time.
harkovskaia [24]

1. The half-life of the element is 22 years

2. The time taken for 308 g of the sample to decay to 4.8125 g is 132 years

<h3>Definition of half-life </h3>

Half-life is simply defined as the time taken for half of a material to decay.

<h3>1. How to determine the half-life </h3>
  • Original amount (N₀) = 45 g
  • Half of the original amount = 45 / 2 = 22.5 g

From the diagram, the time for 22.5 g is 22 years.

Thus, the half-life of the element is 22 years

<h3>2. How to determine the time </h3><h3>i. Determination of the number of half-lives </h3>
  • Original amount (N₀) = 308 g
  • Amount remaining (N) = 4.8125 g
  • Number of half-lives (n) =?

2ⁿ = N₀ / N

2ⁿ = 308 / 4.8125

2ⁿ = 64

2ⁿ = 2⁶

n = 6

<h3>ii. Determination of the time </h3>
  • Number of half-lives (n) = 6
  • Half-life (t½) = 22 years
  • Time (t) =?

t = n × t½

t = 6 × 22

t = 132 years

See attached photo for diagram

Learn more about half life:

brainly.com/question/26374513

5 0
2 years ago
Vocabulary-what is a fossil
Komok [63]
the remains or impression of a prehistoric organism preserved in petrified form or as a mold or cast in rock.
7 0
3 years ago
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A sled is at rest at the top of a slope 2 m high. The sled has a mass of 45 kg. What is the sled’s potential energy? (Formula: P
olga_2 [115]

Explanation:

Gravitational potential energy

= mgh = (45kg)(9.81N/kg)(2m) = 882J.

4 0
3 years ago
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What are the tiny particles that makes up all matter around us?
MakcuM [25]
They are called atoms
5 0
3 years ago
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