Name: ___________________________________ Date: ______________ Practice Test #3 ____ 1. When a precipitation reaction occurs, the ions that do not form the precipitate A) evaporate B) are cations only C) form a second insoluble compound in the solution D) are left dissolved in the solution E) none of these 2. An aqueous solution of potassium chloride is mixed with an aqueous solution of sodium nitrate. The complete ionic equation contains which of the following species (when balanced in standard form)? A) B) C) D) E) ____ 3.
DATE: 10/2/2012 LAB 3 – PHYSICAL & CHEMICAL PROPERTIES *Adapted from LabPaq Purpose: To determine whether certain changes in matter are chemical or physical, and to describe the changes in detail using observational skills Observations and Experimental Data: Substance: Mg Color: Silver Odor: Slighty Effect of Heat: Particles moved, bubbles flowing up to top Solub. or Reaction w/cold H2O: No reaction Solub. or Reaction w/hot H2O: Bubbles produced from the gas Litmus test: Red turned blue and blue had no change Dilute HCl: Sizzle, steams, heat output Dilute NaOH: Gas was formed. Substance: Cu Color: Redish Brown Odor: None Effect of Heat: Became darker, almost purple like. Solub.
D) It conducts electricity when dissolved in water. E) none of the above 4. In a Lewis dot structure the electrons which complete an octet but are not located between two atoms are referred to as A) bonding pairs. B) delta minus electrons. C) excess electrons.
D) the absence of charged molecules inside cells. Answer: C Page Ref: Section 3 11) The ________ pressure is the pressure required to prevent the flow of solvent through a solvent-permeable membrane that separates two solutions of different solute concentration. A) hydrostatic B) electromotive Answer: C Page Ref: Section 3 12 C) osmotic D) partial 12) Which is true about the solubility of electrolytes in water? A) They are all insoluble in water. B) They are usually only sparingly soluble in water.
This is evident because the substance tested positive for both the acid test and the base test for zinc hydroxide. Observations of the zinc and iodine reaction without acetic acid: After swirling, the solution starts off to be yellow, than changes to orange. During swirling becomes dark brown- reddish. The tube feels warm, which means that the reaction is exothermic. Soon, the dark red changes into black and then eventually lighter and lighter becomes colorless.
Also a very pale purple tint formed. Acid test: Added 2 mL of 1M NaOH- no Physical change was observed. Base test: Added 2 mL of .17M Acetic acid- No physical change observed. Table: Zinc (g) | Iodine (g) | Deionized water (mL) | Weight of boiling tube (g) | 1M NaOH(mL) | .17M Acetic acid (mL) | 2 | 2.01 | 5 | 40.73 | 2 | 2 | 2. Answer to focus question: Since it is amphoteric, it will act as an acid if reacts with base and act as a base when reacts with acid.
Observations: Quantitative & Qualitative Data Table Table 1: Solubility Qualitative data: Substances | Time (s) | Soluble or not? (Yes/No) | X | 42 | Yes | Y | 63 | Yes | Z | >180 | No | Table 2: Appearance of the substances while melting Substance X- White rocky powdery dots Qualitative data: Time (s) | Physical appearance of substance X | 10 | White powder dots | 26 | White powder dots | 44 | White powder dots | 55 | White powder dots | 65 | The color of the white powder dots changes to brown powder dots | 82 | Starts to melt a tiny bit | 107 | It stops melting, and there are still white powder left | 125 | Stays as white powder, no melting | 155 | White powder dots, nothing happens | 178 | White powder dots, no melting | 183 | White powder dots, nothing happens | 207 | A few of the tiny white dots starts to melt again | 230 | The white powder stops finally stay still | Table 3: Appearance of the substances while melting Substance Y- White crystal dots Qualitative data: Time (s) | Physical appearance of substance Y | 3 | White crystal dots | 20 | White crystal dots, no change | 40 | White crystal dots, no physical change
Out of all the acids that passed through, only one was found to be toxic. By using high performance liquid chromatography, a polar and nonpolar stationary phase that contained the toxin was mixed, and this isolated the toxin by itself. To ensure that that was the isolated toxin, they further broke it down to find its charge, size, and molecular shape. Mass spectrometry was then used to find the weight and formula of the toxin. By finding the formula, it had similar characteristics to an amino acid known as domoic acid.
In each part of the experiment, you will be observing a different property of electrolytes. Keep in mind that you will be encountering three types of compounds and aqueous solutions: Ionic Compounds These are usually strong electrolytes and can be expected to 100% dissociate in aqueous solution. Example: NaNO 3 (s) → Na+(aq) + NO 3 –(aq) Molecular Compounds These are usually non-electrolytes. They do not dissociate to form ions. Resulting solutions do not conduct electricity.
The mass of zinc will be so small and insignificant that I won’t have any effect on the water, therefore density can’t be calculated. 3. Here is the multiple choice question. Choose one or more of the following statements that is always true about the meaning of 7.14 g/ml. D. 7.14g of zinc occupies 1ml in volume.