Question

2. What is a precipitate and how can it be easily removed from a solution 3. What is the difference between a qualitative and quantitative test? 4. What is the density of a 15 ml solution whose mass is 25 grams? 5. What is the density of a 32 gram cube with a side length of 8.0 cm? 6. Using the graph below, what is the percent by mass of sugar of a solution whose density is 1.035 g/mL? Figure 1: Density vs. % by mass y = 0.00 +0.995 25 10 15 20 5

Answer 1

Precipitate is a solid substance which is insoluble from the solvent and emerges from the solution.

It can be removed from the solution by adding a suitable reagent.

For example when barium chloride is added to solution containing sulphate ion, barium sulfate is precipitated and it can be seperated by filteration.

3) Qualitative analysis involves identification of substance or constituents present in the sample.

Quantitative analysis involves finding of amount of substance present in the sample. It can be done by either volumetric analysis or gravimetric analysis or by any other means.

4) Density is the amount of substance present in a given volume of sample.

Density = Mass/volume

= 25 grams/15 mL

= 1.67 g/mL

5) Volume of a cube = a^{​​​​​​3}​​​​​ where a is the edge length

= 8³ cm^{​​​​​3} = 512 cm^{​​​​​3} = 512 mL

Mass of the cube = 32 grams

Density of the cube = 32 grams/512 mL

= 0.0625 g/mL

6) Fitted line of the plot is Y = 0.003x +0.995

Given that density = 1.035 g/mL

1.035 = 0.003x+0.995

0.003x = 1.035-0.995 = 0.04

X = 0.04/0.003 =13.33%(w/w)