Answer: Option (d) is the correct answer.
Explanation:
A reaction in which heat is absorbed by the substance or reactant molecules is known as an endothermic reaction. In this process energy of reactants is less than the energy of products.
Whereas a reaction in which heat is released by the substance or reactant molecules is known as an exothermic reaction. In this process energy of reactants is more than the energy of products.
For example, when ice is warmed then heat is absorbed by ice molecules due to which there occurs decrease in its intermolecular forces. As a result, ice changes into water.
Therefore, we can conclude that if ice is warmed and becomes a liquid, then it is an endothermic process.
Answer:
Label
Explanation:
You need to search if the chemical need a glass or plastic container. Also if the chemical need to be in a clear or dark container that can protect it from light. Also if need to be a certain temperature, for example, if need to be in the fridge or can be at room temperature.
Most important is that you need to label with the name, formula, date, and if you have the number of lot and the expiration date.
B. Carbon and Silicon
C. Argon and Chlorine
D. Potassium and Calcium
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Answer:
Option-B (Carbon and Silicon)
Explanation:
Among the given pairs only carbon and silicon have the most similar properties. This is because,
Sodium and Magnesium belong to different groups. Sodium present in Group I has one electron in its valence shell and capable of transferring only one electron while, Magnesium present in Group II have two electrons in its valence shell and is capable of donating two electrons. Hence, both show different properties.
Example:
2 Na + Cl₂ → NaCl
Mg + Cl₂ → MgCl₂
As shown in reactions when Sodium and Magnesium are treated with Cl₂ they give a products with different proportions.
Carbon and Silicon show almost same properties because both belong to Group IV hence both are capable of forming four bonds. Also, they share the same property of self linkage in making a long chains.
Argon and Chlorine also belong to two different groups. Argon is present in Group VIII (Noble Gases) and Chlorine is present in Group VII (Halogens). Hence, Argon is an inert specie which is non reactive while Chlorine gives different reaction easily.
Potassium and Calcium belong to different groups. Potassium present in Group I has one electron in its valence shell and capable of transferring only one electron while, Calcium present in Group II have two electrons in its valence shell and is capable of donating two electrons. Hence, both show different properties.
Example:
2 K + Cl₂ → KCl
Ca + Cl₂ → CaCl₂
As shown in reactions when Potassium and Calcium are treated with Cl₂ they give a products with different proportions.
(2) the beaker to the air
(3) the water to the ice cubes
(4) the water to the beaker
Answer:
a) Let's balance the chemical equation for the reaction between HCl and HNO3 to form NOCl, Cl2, and H2O:
First, write the unbalanced equation:
HCl + HNO3 → NOCl + Cl2 + H2O
Now, balance it step by step:
1. Balance the atoms other than hydrogen and oxygen:
HCl + HNO3 → NOCl + Cl2 + H2O
1 1 1
2. Balance the oxygen atoms by adding water (H2O):
HCl + HNO3 → NOCl + Cl2 + H2O
1 1 1 +1
3. Balance the hydrogen atoms by adding HCl on the left side:
HCl + HNO3 → NOCl + Cl2 + H2O
1 1 +1 1 +1
4. Balance the chlorine atoms by adding Cl2 on the left side:
HCl + HNO3 → NOCl + Cl2 + H2O
1 1 +1 1 +1
Now, the equation is balanced.
b) Let's balance the chemical equation for the reaction between CO and I2O5 to form CO2 and I2:
First, write the unbalanced equation:
CO + I2O5 → CO2 + I2
Now, balance it step by step:
1. Balance the atoms other than carbon and oxygen:
CO + I2O5 → CO2 + I2
1 1
2. Balance the oxygen atoms by adding CO2 on the left side:
CO + I2O5 → CO2 + I2
1 1 +2
3. Balance the carbon atoms by adding CO on the left side:
CO + I2O5 → CO2 + I2
1 +1 +2
4. Balance the iodine atoms by adding I2 on the left side:
CO + I2O5 → CO2 + I2
1 +1 +2 +5
Now, the equation is balanced.