How much hot solvent should be used to dissolve the solids?单项选择题
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After the solid has dissolved, it is better to wait until the solution has reached room temperature before placing the system in an ice bath.
Recrystallisation is a very important technique in synthetic chemistry. A critical step is in selecting a solvent system where the impurities are very soluble but the product is only partly soluble. The mixture for purification is heated to dissolve all of the product in a super saturated solution. On cooling the product starts to crystallise out of solution as it's solubility is poor at room temperature. If you have chosen your solvent correctly your impurity will stay in solution. Watch this short video and answer the following questions about recrystallisation. Note: this is an example recrystallisation and not actually a benzocaine recrystallisation. Recrystallisation video Why do we allow our recrystallisation to cool slowly? Please select the most accurate answer.
Recrystallisation is a very important technique in synthetic chemistry. A critical step is in selecting a solvent system where the impurities are very soluble but the product is only partly soluble. The mixture for purification is heated to dissolve all of the product in a super saturated solution. On cooling the product starts to crystallise out of solution as it's solubility is poor at room temperature. If you have chosen your solvent correctly your impurity will stay in solution. Watch this short video and answer the following questions about recrystallisation. Note: this is an example recrystallisation and not actually a benzocaine recrystallisation. Video Player is loading.Play VideoPlaySkip BackwardSkip ForwardMuteCurrent Time 0:00/Duration 0:00Loaded: 0%Stream Type LIVESeek to live, currently behind liveLIVERemaining Time -0:00 1xPlayback Rate2x 1.75x 1.5x 1.25x 1x, selected 0.75x 0.5x ChaptersChapters Descriptionsdescriptions off, selected Captionscaptions and subtitles off, selected Audio TrackPicture-in-PictureFullscreenThis is a modal window.Beginning of dialog window. Escape will cancel and close the window.TextColor[select: White, Black, Red, Green, Blue, Yellow, Magenta, Cyan]Opacity[select: Opaque, Semi-Transparent]Text BackgroundColor[select: Black, White, Red, Green, Blue, Yellow, Magenta, Cyan]Opacity[select: Opaque, Semi-Transparent, Transparent]Caption Area BackgroundColor[select: Black, White, Red, Green, Blue, Yellow, Magenta, Cyan]Opacity[select: Transparent, Semi-Transparent, Opaque]Font Size[select: 50%, 75%, 100%, 125%, 150%, 175%, 200%, 300%, 400%]Text Edge Style[select: None, Raised, Depressed, Uniform, Drop shadow]Font Family[select: Proportional Sans-Serif, Monospace Sans-Serif, Proportional Serif, Monospace Serif, Casual, Script, Small Caps]ResetDoneClose Modal DialogEnd of dialog window. Why do we allow our recrystallisation to cool slowly? Please select the most accurate answer.
Section A: Read the text and answer the questions. Brutalism is an architectural style, introduced in the 1950s. It uses exposed concrete to create geometric structures with a grey appearance. Concrete buildings are often criticised as cold and ugly, lacking the warmth of stone or the smooth feel of steel. However, concrete, as a building material, has unique characteristics. It is extremely flexible when wet, and is adapted to create interesting shapes. Many urban public buildings, such as universities, have also used concrete as the main material to indicate strength and permanence. Instead of keeping Brutalist buildings, many are being demolished to make space for modern styles. However, this does not acknowledge the cultural history of these buildings, and is not sustainable. Fill in the gap with ONE WORD from the paragraph. 1. Brutalist architecture included exposed concrete, which gave a cold Answer Question 1[input] .
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