Which parts of Dalton’s atomic theory had to be revised

1 answer:

eduard3 years ago

7 0

The indivisibility of an atom was proved wrong an atom can be further subdivided into protons, neutrons and electrons. However an atom is the smallest particle that takes part in chemical reactions

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A child pulls on a wagon with a force of 75 N. If the wagon moves a total of 42 m in 3.1 min, what is the average power delivere

exis [7]

Answer:

16.96 W

Explanation:

Power: This can be defined as the rate at which work is done by an object. The S.I unit of power is Watt(W).

From the question,

P = (F×d)/t....................... Equation 1

Where P = power, F = force, d = distance, t = time.

Given: F = 75 N, d = 42 m, t = 3.1 min = 3.1×60 = 186 s

Substitute these values into equation 1

P = (75×42)/186

P = 16.94 W

Hence the average power delivered by the child = 16.96 W

4 0

3 years ago

If 200 ml of tea at 90 °C is poured into a 400 g glass cup initially at 25 °C, what would be the final temperature of the mixtur

sweet-ann [11.9K]

The final temperature of the mixture is 43.62 °C

To solve the question above, we apply the law of calorimetry

The law of calorimetry: which states that if there is no lost of heat the surrounding, heat lost is equal to heat gained, or it can be stated as heat absorbed by a cold body is equal to heat released by a hot body, provided there is no lost of heat to the surrounding.

The law above is expressed mathematically as

Cm(t₁-t₃) = C'm'(t₃-t₂)............. Equation 1

Using equation 1 to solve the question,

Let: C = specific heat capacity of glass cup, m = mass of glass cup, C' = specific heat capacity of tea, m' = mass of tea, t₁ = initial temperature of tea, t₂ = initial temperature of glass cup, t₃ = final temperature of the mixture.

From the question,

Given: m = 400 g = 0.4 kg, C = 840 J/kg°C, m' = 200g (tea is a liquid made of water and the volume of water in ml is thesame a its mass in gram) = 0.2 kg, C' = 4186 J/kg.°C, t₁ = 90°C, t₂ = 25°C

Substitute these values into equation 1 and solve for t₃

0.4(840)(90-t₃) = 0.2(4186)(t₃-25)

336(90-t₃) = 837.2(t₃-25)

30240-336t₃ = 837.2t₃-20930

collect like terms

837.2t₃+336t₃ = 30240+20930

1173.2t₃ = 51170

t₃ = 51170/1173.2

t₃ = 43.62 °C

Hence, the final temperature of the mixture is 43.62 °C

7 0

3 years ago