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Do you groan when you read “story problems?” You may have to write a balanced equation from the words in a story problem. The next chapter has questions like this: 56.0 g of aluminum reacts with excess copper(II) nitrate. How much copper is produced? This may sound scary, but remember the following tips to help you meet the challenge. 
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For the time being let’s ignore the 56.0 g and focus on finding the balanced equation. There are helpful key words. It says aluminum reacts with copper(II) nitrate. These substances must be reactants and on the left side of the arrow. The combination of products helps you see what kind of reaction will take place.
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The problem goes on to say that copper is produced. Therefore copper is a product and on the right side of the arrow. So far it looks like aluminum and nitrate have disappeared. They are not mentioned as products in the problem. However, from the law of conservation of mass we know they must still be present.
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To find out where the missing aluminum and nitrate belong, we need to determine what type of reaction is taking place.
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A single element and a compound react to form at least copper, that must mean the other product is a compound. This must be a single replacement reaction. Therefore, the aluminum and nitrate are like the A and X and should be together in a compound on the right. Aluminum has a positive three charge and nitrate has a negative one charge. Therefore, one aluminum needs three nitrates to balance the charge.
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Now that we have the same kinds of atoms on both sides of the equation, the last step is to balance the equation.
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We can now deal with the 56.0 g. But why don’t we leave that for the next chapter!
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Given the following reactants in a double replacement reaction, predict the products and balance the equation. Cr(NO3)3 + Rb2CO3 →
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2Cr(NO3)3 + 3Rb2CO3 → Cr2(CO3)3 + 6RbNO3
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