1) Metals that are above hydrogen in the reactivity series react with dilute hydrochloric acid to produce hydrogen gas. Lead is just above hydrogen in the reactivity series.I read a book that says no reaction occurs between lead & dilute acid. Why? Is it because the reaction is too slow?
2) Magnesium + Iron (II) Chloride gives Magnesium chloride + iron. What colour is the iron solid? Black?
3)When reacting a metal with steam, the delivery tube must be removed from the water in the trough before turning off the Bunsen flame. This is to prevent water from being sucked back into the hot test tube. Why will water be sucked back into the hot test tube?
Thank you!
1) Metals that are above hydrogen in the reactivity series react with dilute hydrochloric acid to produce hydrogen gas. Lead is just above hydrogen in the reactivity series.I read a book that says no reaction occurs between lead & dilute acid. Why? Is it because the reaction is too slow?
It is slow but one of the reasons why it is so slow (and some may say actually doesn't react) is because the surface atoms of Pb react with the HCl to form PbCl2. It just happens that PbCl2 is not soluble in water and even less soluble in HCl. Therefore, the first layer of Pb atoms do react, forming a coating of PbCl2, and that hinders further reaction.
2) Magnesium + Iron (II) Chloride gives Magnesium chloride + iron. What colour is the iron solid? Black?
Yes, finely divided iron is black.
3)When reacting a metal with steam, the delivery tube must be removed from the water in the trough before turning off the Bunsen flame. This is to prevent water from being sucked back into the hot test tube. Why will water be sucked back into the hot test tube?
Remember Charles' Law (volume vs temperature). When the gases in the heated tube cool, the volume contracts, that causes the pressure to drop and that causes the liquid to be sucked into the heated tube. Actually, you can skip the volume part and just remember that pressure decreases with decreasing temperature. When the temperature of the heated tube cools, the pressure is decreased, and the water is sucked in to equalize the pressure.
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1) The lack of reaction between lead and dilute hydrochloric acid is not primarily due to the reaction being too slow. It is because lead is below hydrogen in the reactivity series. In the reactivity series, metals are arranged in order of their reactivity, with the most reactive ones at the top. When a metal is above hydrogen in the reactivity series, it will react with dilute acid and displace hydrogen gas. However, if a metal is below hydrogen, like lead, it will not react with dilute acid because it is less reactive than hydrogen.
To determine the reactivity series, you can refer to a reliable source like a chemistry textbook or conduct experiments to compare the reactivity of different metals. The reactivity series is essential in predicting the behavior of metals in various chemical reactions.
2) The iron solid obtained from the reaction between magnesium and iron(II) chloride is indeed black. This is because the iron produced in this reaction is in the form of iron(II) chloride, which generally appears black. The reaction between magnesium and iron(II) chloride leads to the displacement of iron, resulting in the formation of magnesium chloride and iron as a solid precipitate. The color of the resulting iron solid can vary depending on other factors such as impurities, oxidation states, and crystal structure.
To confirm the color of the iron solid in a specific reaction, it is advisable to refer to reliable sources, perform experiments, or consult chemistry references such as textbooks or databases.
3) Water is likely to be sucked back into the hot test tube when the delivery tube is not removed from the water in the trough before turning off the Bunsen flame because of the process called the condensation vacuum.
When a test tube containing steam is heated, the steam expands and displaces the air from the test tube. The delivery tube connected to the test tube serves as a channel for the gas to escape into the water in the trough. This process creates a partial vacuum inside the test tube.
If the Bunsen flame is turned off before removing the delivery tube from the water, the steam inside the test tube starts to cool down. As the steam cools, it loses its volume and creates a partial vacuum inside the test tube. This partial vacuum causes atmospheric pressure to push water back into the test tube through the delivery tube, resulting in water being sucked back.
To prevent water from being sucked back, it is crucial to remove the delivery tube from the water in the trough before turning off the Bunsen flame. By doing so, you break the connection between the test tube and the water, preventing any water from being drawn into the test tube due to the condensation vacuum.