How can you check the purity of the generated hydrogen? How does a mixture of hydrogen and air burn?

How can you check the purity of the generated hydrogen? How does a mixture of hydrogen and air burn? How does pure hydrogen burn? Write the equation for the reaction of burning hydrogen.

To check the hydrogen for purity, we carefully bring the test tube with hydrogen turned upside down to the burner flame. If pure hydrogen is collected, then it burns calmly and the characteristic sound “p-lakh” is heard. If hydrogen contains an admixture of air, then it burns with a characteristic whistling pop
2H2 + O2 -> 2H2O

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