@media only screen and (max-width: 767px) {
    #muc-chung .col-md-6 {
        text-align: center;
    }

     #muc-chung .col-md-6 iframe{
        width: 100%;
    }

    #muc-chung .container {
        width: 90%;
        padding: 0 5%;
        max-width: 420px;
    }
}