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How do you balance a chemical equation?
A balanced equation has the same number of each type of atom on both sides. Count the atoms of each element, then change the large numbers in front of formulas…
How do you calculate the number of moles?
Number of moles = mass ÷ molar mass, written n = m ÷ M. Use the mass in grams and the molar mass in g/mol, which you get by adding the relative atomic masses from the…
What is the difference between ionic and covalent bonding?
Ionic bonding happens between a metal and a non-metal: the metal transfers electrons to the non-metal, forming oppositely charged ions that attract each other. Covalent…
What is pH and how is it measured?
pH is a scale from 0 to 14 that shows how acidic or alkaline a solution is. Below 7 is acidic, 7 is neutral and above 7 is alkaline. It is measured with universal…
How is the periodic table arranged?
Elements are arranged in order of increasing atomic number (the number of protons). Columns are called groups: elements in the same group have the same number of…
What factors affect the rate of a chemical reaction?
The rate of reaction increases with higher temperature, higher concentration (or pressure for gases), larger surface area and the presence of a catalyst. Collision…
What is the difference between exothermic and endothermic reactions?
An exothermic reaction gives out energy to the surroundings, usually as heat, so the temperature rises. An endothermic reaction takes in energy from the surroundings, so…
How does electrolysis work?
Electrolysis uses electricity to break down an ionic compound that is molten or dissolved, called the electrolyte. Positive ions move to the negative electrode (cathode)…