number 4 Chemistry 101 87 Tear this page out of your laboratory manual and submi
ID: 587985 • Letter: N
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number 4
Chemistry 101 87 Tear this page out of your laboratory manual and submitted to your TA with your answers B. Post-Lab Assessment Questions: (23 pts) 1. (3 pts) Categorize the solids you tested today as pure substance or mixtures 2. (3 pts) Categorize the pure substances you tested today elements vs compounds and metals vs non-metals 3. In the lab today you prepared oxygen gas by decomposing hydrogen peroxide. There are many other chemical reactions that generate gases as one of their products. Lets consider the reaction between zinc metal and hydrochloric acid as such an example a) (2 pts) What are the products of the chemical reaction that occurs when zinc metal is added to an aqueous solution of Hydrochloric acid? b) (3 pts) Write the chemical equation that represents this reaction? c) (4 pts) write a procedure that explains how you would collect the gas produced from this reaction in the laboratory 4. Imagine that you are given two metal oxides to study in the lab. You heat each oxide in a small test tube and then insert a glowing splint into each. You observe that the splint in tube 1 immediately ignites and burns with a steady flame before it dies, but the splint in tube 2 does not. a) (2 pts) What happened to the metal oxide in tube 1 when it was heated? b) (4 pts) Do both metal oxides decompose when heated? Provide evidence to support your answer. (2 pts) What can you conclude about the stability of the 2 oxides based on these observations? c) boratory Experiment9Explanation / Answer
When a metal oxide is heated it may or may not be decomposed into metal and oxygen. Some metal oxides decompose into metal and oxygen as follows
MxOy---> Mx + y/2 O2
Some metal oxides do not decompose as above and remains as same.
To know whether metal oxide is decomposed or not we have to test for oxygen with a blowing splint .If oxygen is evolved in a test tube the splint ignites and burns with a steady flame. If no such observation is observed it indicates the absence of oxygen. Therefore we can answer the three questions of part 4 easily as follows.
a) the metal oxide in the first test tube is decomposed into metal and oxygen. Due to the presence of oxygen gas glowing splint is ignited and burns with steady flame.
a) no. Both oxides are not decomposed. If both are decomposed then both oxides respond similarly with blowing splint. The metal oxide in second test tube is not decomposed because blowing splint was not ignited when placed on this test tube due to the absence of oxygen gas.
C) if a metal oxide decomposes into it's constituents on heating, that metal oxide is regarded as unstable and if not decomposed on heating that metal oxide is stable. Therefore we can conclude that metal oxide in first tube is unstable and metal oxide in second test tube is stable.
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