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garri49 [273]
3 years ago
8

Heat required to raise 1 g of a substance 1°C

Chemistry
1 answer:
Oksana_A [137]3 years ago
7 0

Answer:

Specific heat

Explanation:

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A 25.0-mL sample of 0.150 M hydrazoic acid, HN3, is titrated with a 0.150 M NaOH solution. What is the pH after 13.3 mL of base
tamaranim1 [39]

Answer:

pH ≅ 4.80

Explanation:

Given that:

the volume of HN₃ = 25 mL = 0.025 L

Molarity of HN₃ = 0.150 M

number of moles of HN₃ = 0.025 × 0.150

number of moles of HN₃ =  0.00375  mol

Molarity of NaOH = 0.150 M

the volume of NaOH = 13.3 mL = 0.0133

number of moles of NaOH = 0.0133× 0.150

number of moles of NaOH = 0.001995 mol

The chemical equation for the reaction of this process can be written as:

HN_3 + OH- ---> N^-_{3} + H_2O

1 mole of hydrazoic acid react with 1 mole of hydroxide to give nitride ion and water

thus the new number of moles of HN₃ = 0.00375 - 0.001995 = 0.001755 mol

Total volume used in the reaction =  0.025 +  0.0133 = 0.0383  L

Concentration of HN_3 = \dfrac{0.001755}{0.0383} = 0.0458 M

Concentration of N^{-}_3 = \dfrac{ 0.001995 }{0.0383} = 0.0521 M

GIven that :

Ka = 1.9 x 10^{-5}

Thus; it's pKa = 4.72

pH =4.72 +  log(\dfrac{ \ 0.0521}{0.0458})

pH =4.72 + log(1.1376)

pH =4.72 + 0.05598

pH =4.77598

pH ≅ 4.80

3 0
3 years ago
How would a collapsing universe affect light emitted from clusters and superclusters? A. Light would acquire a blueshift. B. Lig
Lady_Fox [76]

Answer:

Choice A: Light would acquire a blueshift.

Explanation:

When a universe collapses, clusters of stars start to move towards each other. There are two ways to explain why light from these stars will acquire a blueshift.

Stars move toward each other; Frequency increases due to Doppler's Effect.

The time period t of a beam of light is the same as the time between two consecutive peaks. If \lambda is the wavelength of the beam, and both the source and observer are static, the time period T will be the same as the time it takes for light travel the distance of one \lambda (at the speed of light in vacuum, c).

\displaystyle t = \frac{\lambda}{c}.

Frequency f is the reciprocal of time period. Therefore

\displaystyle f = \frac{1}{t} = \frac{c}{\lambda}.

Light travels in vacuum at a constant speed. However, in a collapsing universe, the star that emit the light keeps moving towards the observer. Let the distance between the star and the observer be d when the star sent the first peak.

  • Distance from the star when the first peak is sent: d.
  • Time taken for the first peak to arrive: \displaystyle t_1 =\frac{d}{c}.

The star will emit its second peak after a time of. Meanwhile, the distance between the star and the observer keeps decreasing. Let v be the speed at which the star approaches the observer. The star will travel a distance of v\cdot t before sending the second peak.

  • Distance from the star when the second peak is sent: d - v\cdot t.
  • Time taken for the second peak to arrive: \displaystyle t_2 =t + \frac{d - v\cdot t}{c}.

The period of the light is t when emitted from the star. However, the period will appear to be shorter than t for the observer. The time period will appear to be:

\begin{aligned}\displaystyle t' &= t_2 - t_1\\ &= t + \frac{d - v\cdot t}{c} - \frac{d}{c}\\&= t + (\frac{d}{c} - \frac{v\cdot t}{c}) -\frac{d}{c}\\&= t - \frac{v\cdot t}{c} \end{aligned}.

The apparent time period t' is smaller than the initial time period, t. Again, the frequency of a beam of light is inversely proportional to its period. A smaller time period means a higher frequency. Colors at the high-frequency end of the visible spectrum are blue and violet. The color of the beam of light will shift towards the blue end of the spectrum when observed than when emitted. In other words, a collapsing universe will cause a blueshift on light from distant stars.

The Space Fabric Shrinks; Wavelength decreases as the space is compressed.

When the universe collapses, one possibility is that clusters of stars move towards each other. Alternatively, the space fabric might shrink, which will also bring the clusters toward each other.

It takes time for light from a distant cluster to reach an observer on the ground. The space fabric keeps shrinking while the beam of light makes its way through the space. The wavelength of the beam will shrink at the same rate. The wavelength of the beam of light will be shorter by the time the beam arrives at its destination.

Colors at the short-wavelength end of the visible spectrum are blue and violet. Again, the color of the light will shift towards the blue end of the spectrum. The conclusion will be the same: a collapsing universe will cause a blueshift on light from distant stars.

8 0
2 years ago
why is H2SO4 considered as strong acid? What colour does it give with phenolphthalein and methyl orange?​
marta [7]

Answer:

H2SO4 (sulphuric acid) is considered a strong acid because it's H+ ions completely dissociates or ionizes in a water. When reacted with phenolphthalein is colourless because phenolphthalein doesn't react with acids, only strong bases and when reacted with methyl orange, it changes from orange to red.

Explanation:

4 0
2 years ago
Which of these scientists diagnosed smallpox and measles?
kotykmax [81]
......................B. Al-Razi
5 0
2 years ago
List a few ways that would lead you to believe a chemical reaction has occurred
iren2701 [21]
There are many ways which can <span>lead us to believe a chemical reaction has occurred. I am discussing few of them.

Change in Color:
                          Few reactions proceed with the change in colour. When Bromine Water (yellow-Brown) is treated with unsaturated compounds, the color disappear as the reaction is completed.

Gas Production:
                         Some reactions proceed with the elimination of gas i.e. CO</span>₂ , H₂, N₂, H₂O e.t.c. 

Temperature Change:
                                 Some reactions evolve or absorb heat when proceed. This change is the evidence of progress of reaction.

Thin Layer Chromatography:
                                             Very important technique in detecting the progress of reaction by determining the number of spots for UV active compounds on TLC plate. Even non UV active compounds can be detected by using other locating agents.

Instrumental Techniques:
                                       Modern techniques like IR, MS, NMR, UV spectroscopy can be used to detect the progress of reaction.
5 0
3 years ago
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